Archive for the ‘Geology’ Category

Visiting Zion National Park: Part I   20 comments

Zion Canyon from Bridge Mountain.

Zion Canyon from Bridge Mountain.

I’m going to change pace and do a short travel series: an in-depth look at Zion National Park.  I’ve not done one of these for a long time.  As usual I’ll start with Zion’s natural history, including geology in this post.  Then I’ll go on to human history and life on display at Zion.  I’ll finish with travel logistics and recommendations for various visit lengths, focusing of course on photography.

If you haven’t yet visited Zion, this series will be an in-depth introduction with tips, but without presuming to tell you exactly where and how to photograph the park.  If you’ve been to Zion before, you will learn some interesting stuff about the park and probably find out about one or two out-of-the-way photo spots.

But mostly this is about background knowledge.  I strongly believe the more you know about a place the better your experience and photos will be.  Though my posts are always heavily illustrated, I hope you’ll try to forget the pictures when you go out yourself.  Do your own thing and get pictures that represent your own unique take on the park.

East Temple from just east of the tunnels.

East Temple from just east of the tunnels.

REGIONAL SETTING

Zion National Park lies in southwestern Utah, in an area called Dixie.  That term is normally associated with the southern states (Alabama, Georgia, etc.).  Utah’s Dixie is certainly where the climate is warmest in the Beehive State.  But it’s much drier than the humid South.  Zion is at the southwestern edge of the Colorado Plateau, that huge regional uplift of sedimentary rocks that covers parts of four states and defines much of the dramatic scenery of America’s desert southwest.

THE GRAND STAIRCASE

Zion is also on the western edge of a geologic feature called Grand Staircase.  This is a large series of cliff-forming sedimentary layers that steps downward from north to south.  Some of the area’s highest and youngest rocks are to the north near Bryce Canyon while some of the lowest and oldest rocks are exposed to the south in Grand Canyon.

But the rim of that last southern step (it’s a doozie!) tops out at 8800 feet in elevation on the north rim of the Grand Canyon.  That’s very similar to the top of Bryce (the northern step) at 9100 feet.  So the Grand Staircase not so much steps downward in elevation but in geology.

BREAKS & CANYONS

Zion Canyon, centerpiece of the park, plus Cedar Breaks to the north, are located where the land “breaks” downward off the high eastern plateaus of south-central Utah to meet the lower deserts of SW Utah and southern Nevada.  These breaks are also known as the Hurricane Cliffs, which continue south into NW Arizona.

The towns in this part of Utah, largest of which is St. George, are situated near the foot of this dramatic sandstone escarpment, at a relatively low elevation compared with much smaller burgs up in the plateau country to the east.  The Virgin River and its tributaries have cut generally SW-facing canyons down through the escarpment.  The most dramatic of these is Zion Canyon.

The Hurricane Cliffs 'break' down off the Colorado Plateau here at Kolob Canyons, part of Zion National Park, Utah.

The Hurricane Cliffs ‘break’ down off the Colorado Plateau here at Kolob Canyons, part of Zion National Park, Utah.

The lower terrain near St. George, Utah is exemplified by Snow Canyon State Park, but the land continues to drop to the south and west.

The lower terrain near St. George, Utah is exemplified here at Snow Canyon State Park, but the land continues to drop to the south and west.

GEOLOGIC HISTORY

THE GREAT JURASSIC DESERT

The most prominent formation at Zion is Navajo Sandstone.  It forms most of the named dome-like features at Zion, such as the Patriarchs, the Sentinel, and White Throne.  The Navajo, which is generally a whitish sandstone, preserves record of an ancient desert.  This desert, which existed in the Jurassic age (dinosaur times), was dominated by enormous sand dune fields (ergs) similar to today’s Sahara Desert.

You can tell the rocks are ancient sand dunes because of cross-bedding.  Take a good look at the sandstone walls at Zion and notice the lines angled at about 35 degrees to the main rock layers, which are nearly horizontal.  A great place to see cross-bedding is at Checkerboard Mesa near the park’s east entrance, but you’ll see it everywhere in East Zion east of the tunnels.  The rocks behind the sheep below show cross-bedding.

Desert bighorn sheep at East Zion.

Desert bighorn sheep at East Zion.

The desert sands of the Navajo formed when plate tectonics, beginning a couple hundred million years ago, dragged this area north from equatorial to much drier latitudes in the vicinity of the Tropic of Cancer (30 degrees north).  This is the latitude, both north and south of the equator (Tropic of Capricorn), where the world’s major deserts are still found.

Also contributing to desertification in the Jurassic were the mountains building to the west of Zion in Nevada and California.  These ranges, which were the result of tectonic collision at the western edge of North America, are now gone, eroded away.  But in the Jurassic they formed an effective rain-shadow, blocking rains coming off the Pacific and helping to dry things even further.

A side-canyon in East Zion has a stream carrying sand eroded from the Navajo Sandstone, itself built from dune sands eroded from a long-gone ancient mountain range.

A side-canyon in East Zion has a stream carrying sand eroded from the Navajo Sandstone, itself built from dune sands eroded from a long-gone ancient mountain range.

PRE-DESERT TIMES

There is more than Navajo Sandstone at Zion, however.  The Virgin River has cut so deeply into the rocks that, despite the great thickness of the Navajo, other formations are visible beneath it.  These record shallow seas, meandering streams and floodplain environments.  For example, the Kayenta and Moenave Formations below the Navajo are reddish stream deposits formed in climates that changed from subtropical (for the older Moenave) to semi-arid (for the overlying Kayenta).

These older formations form the rubbly slopes and red cliff bands low on Zion’s canyon walls.  They’re also prominent above the town of Springdale, and up on Kolob Terrace Road.  Solid red cliffs of Kayenta, formed at the edge of that great encroaching desert, lie directly beneath the hard white sandstones of the Navajo.

If you gain a high vantage point you may notice the red “hats” or caps on top of the Navajo Formation’s highest white domes.  These belong to the Temple Cap and Carmel Formations, at 160 million years the youngest rocks at Zion.  Their reddish color is clue to wetter conditions returning in the late Jurassic.  A warm sea even invaded again, this signaled by limestones of the Carmel Formation.

The Navajo Sandstone is in places stained with iron oxide, where fractures have allowed fluids to penetrate the rock and move iron from other formations.

The Navajo Sandstone is in places stained with iron oxide, where fractures have allowed fluids to penetrate the rock and move iron from other formations.

UPLIFT & EROSION

Time didn’t stop after deposition of the Navajo and other Jurassic rocks at Zion.  Sedimentation continued into the Cretaceous and beyond; yet, save for an important exception (see below), younger rocks of the Zion region have been stripped away by erosion and transported down the Colorado River into the Pacific Ocean.

Erosion is a big deal at Zion.  The Colorado Plateau continues to be shoved upward by tectonic pressures (a 5.8 magnitude earthquake shook Zion in 1995).  Over time, this uplift has increased river gradients dramatically, resulting in very active erosion by streams and rivers as well as landslides.  Wind has helped sculpt the landscape.

Basaltic lava flows form a stark contrast with iron-stained Navajo Sandstones.

Basaltic lava flows form a stark contrast with iron-stained and dune cross-bedded Navajo Sandstones.

YOUNG LAVA FLOWS

If you drive up to Lava Point on the Kolob Terrace Road, you will notice dark lava flows, which flowed out of vents that opened up as this area began to stretch (rift), starting about 2 million years ago.  This young age places the lava flows (which being basalt were quite fluid) in the Ice Ages, which were fairly wet times at Zion.  Think about the terrain at that time, which was dramatic canyon country as it is today.

This combination of climate, active basaltic volcanism and topography tells you something must have happened (and it did!):  lava-dammed lakes.  If you hike the Subway, a lake formed in that canyon when lava dammed the Left Fork; it extended all the way up to the Subway itself.  If you’re observant you’ll notice fine lake muds and silts laid down by this lake.  You pass right by them when you’re hiking back out of the canyon.

By the way, let’s put some numbers on this story.  Most of what you see at Zion is between about 200 and 160 million years old, placing it squarely in the Mesozoic Era, age of dinosaurs.  Less noticeable rocks beneath these are as old as 250 million years, while the young lavas are between 1.5 and 200,000 years old.

Dusk falls on the Kolob Terrace, with a large dome of Navajo Sandstone catching the glow above red Kayenta sandstones. Footprints of sauropods (huge plant-eating dinos) have been found in the red formation.

Dusk falls on Kolob Terrace, with a large dome of Navajo Sandstone catching the glow above steep red and mauve slopes of the Kayenta.  Beneath that in the foreground are brick-red rubbly cliffs of the Springdale Member of the Moenave Formation. Footprints of sauropods (huge plant-eating dinos) have been found here.

TROPICAL SEAS AT ZION?

The older pre-dinosaur strata is worth mentioning because it is prominent at nearby attractions, such as Grand Canyon to the south of Zion.  Most prominent of the area’s oldest rock formations is the Kaibab.  It dates back to Permian times about 260 million years ago.  In these ancient times, an embayment of the ocean we call Panthalassa lapped at the edge of the world’s only landmass, the supercontinent Pangaea.  At that time this region, later to become Utah and Arizona, was near the equator.

The Kaibab is mostly limestone, formed in warm, shallow seas.  It’s visible in places low along the Virgin River within the park and also dramatically in the Hurricane Cliffs near the town of Hurricane and north along the east side of I-15.  It’s interesting to realize that the Kaibab, which hides low in Zion’s deep canyons, forms the high rim of Grand Canyon to the south.  This tells you something about the layout of the Grand Staircase.

Thought I'd throw in a shot from the Grand Canyon, because the Kaibab Limestone is exposed so well here at Toroweap on the North Rim.

Thought I’d throw in a shot from the Grand Canyon, because the Kaibab Limestone is exposed so well here at Toroweap on the North Rim.

THE SENTINEL SLIDE

More recently during the Ice Ages, the climate at Zion was wetter than today’s.  The Virgin and other rivers carried more water, thus flash-flooding was more frequent and violent.  Four thousand years ago a huge landslide blocked the Virgin River and formed a 350 foot-deep lake in Zion Canyon.  This enormous slump block came off The Sentinel, so it’s called the Sentinel Slide.

The lake extended from Canyon Junction all the way to Angel’s Landing.  Sediments settled out on the canyon floor, partly filling its natural V-shape.  The river could not be stopped for long of course, and the natural dam was eventually breached.  The resulting flood drained the lake and formed the V-shaped inner canyon between Court of the Patriarchs and Canyon Junction.

So now you know why Zion Canyon is flat-bottomed; it’s the old lake-bed.  You can see the remains of the Sentinel Slide above you on the left as you drive up-canyon.  For a closer view hike or go on a horse-back ride on the Sand Bench Trail, which climbs up on top of the slump block itself.  By the way, the Sentinel Slide still acts up from time to time.  In 1995, part of the old slide slipped, briefly blocking the river.  The road was flooded for a time until the Virgin, never to be denied for long, re-established its channel.

Stay tuned for more from Zion National Park!

Looking down-canyon at sunset from atop Sand Bench, which is the huge slump block of the Sentinel Slide.

Looking down-canyon at sunset from atop Sand Bench, which is the huge slump block of the Sentinel Slide.  I’m on top of one of the huge blocks moved by the slide.

 

Advertisements

Mountain Monday: Telescope Peak & Death Valley   12 comments

Telescope Peak and the Panamint Range from southern Death Valley's Saratoga Springs.

Telescope Peak and the Panamint Range from southern Death Valley’s Saratoga Springs.

Occasionally I like to highlight a mountain I like for Mountain Monday.  Today it’s Telescope Peak, in Death Valley National Park, California.  This has long been one of my favorite national parks.  I started visiting when it was still a national monument.  My first visit was a college seminar and field trip.  My second time was freelancing with friends, and we climbed Telescope Peak.

The top is just over 11,000 feet high, and since it was early spring, we waded through hip-deep snow drifts to get there.  After the all-day climb, we drove back down into the valley, took our sleeping bags, and tumbled out into the sand dunes to sleep under the stars.  What a contrast!  An icy morning at 8000 feet, a snowy climb, then sleeping out in balmy weather at sea level.

Snow-capped Telescope Peak has been lifted by the range-front fault over 11,000 feet above the floor of Death Valley.

Snowy Telescope Peak has been lifted by faulting along the range-front over 11,000 feet above the hot desert floor of Death Valley.

GEOLOGIC INTERLUDE

Telescope is the highest point in the park and crowns the Panamint Range.  The Panamints are an upraised block of the earth’s crust, lifted along the west side of a fault zone that at the same time dropped Death Valley down.  And down a lot!  The floor of the valley is a few hundred feet below sea level.

But the valley is filled with thousands of feet of sediments that were eroded from the Panamints and other ranges as they rose.  The top of the the bedrock that was dropped down by the fault lies some 11,000 feet beneath the valley floor.  This enormous wedge of valley fill is made of gravels, sands and clays.  But overall it’s quite salty.  There are thick sections of salts of various kinds, including good old NaCl, table salt.

These salt flats at Badwater in Death Valley are just the top of thousands of feet of salt and sediments filling the valley.

Geologists call these types of deposits evaporites because they are formed when large bodies of water evaporate away in a drying climate.  In Death Valley’s case it was a large lake called Lake Manly.  From about 2 million to 10,000 years ago, mega ice sheets lay to the north.  Because of this, the climate was quite wet in the now ultra-dry Death Valley region.  Early hunter-gatherers, recently migrated in from Siberia, were able to spread south because of this climate, which supported a diversity of life much greater than today’s desert does.

But when the ice sheets retreated during inter-glacial periods, the climate grew more arid, and Lake Manly shrank.  Because of how fault-block mountains border almost all sides of Death Valley, often there was little or no chance for the lake to drain in the normal way, via rivers.

The old Death Valley Borax Works, with a heavy-duty wagon.  This wheel is six feet high.

The six-foot high wheel of a heavy duty borax wagon.

Evaporation was (and is) the main way that water left the valley.  Salts that were dissolved in the water grew more concentrated as the lake grew smaller.  A brine was the result, and as the lake grew and shrank many times, often down to nothing, the salts were precipitated out.  They built up layers and layers of evaporite deposits.  The famous 20 mule-team wagon trains transported tons of borax from the borates (a type of salt) mined from the valley (image above).

A close-up of Death Valley’s evaporites (salt deposits).

BADWATER SALT FLATS

The current desert climate of Death Valley is one in which standing water from paltry winter rains evaporates rapidly, leaving behind fresh salt.  The salt can take very interesting forms (image above).  The mix of fine muds and salt, combined with repeated wet/dry cycles, can form fantastic polygonal patterns, as the bottom image shows.  Salt is also eroded away occasionally by the Amargosa River when infrequent storms allow it to flow south out of the valley.

The water in the image at the top of the post is really not part of this equation.  It’s fresh not salty, and comes from the amazingly strong Saratoga Springs in southern Death Valley.  I camped nearby one time and captured this view early the next morning.  Saratoga is well off the beaten track and most visitors to the park miss it.  There’s a very cool dune field nearby.

The salt flats in Death Valley form interesting polygonal patterns.

The salt flats in Death Valley form interesting polygonal patterns.  Telescope Peak is just left off the photo.

Single-image Sunday: Patterns in Sandstone   5 comments

Since the Foto Talk this week was all about not getting too caught up in the search for abstract patterns in your photography, I thought I’d post an image whose sole aim was to abstract the subject.  But is this really an abstract?  I could have made it more so, for example by moving the camera or otherwise blurring details and color.  Or by getting experimental in post-processing.  But I wanted the close-up features of this dune sandstone to be very clear.

The abstraction is created by simply getting  close with my macro lens and framing so as to exclude the tiny flaws that are scattered through the rock.  I captured this at the famous Wave in southern Utah’s Vermilion Cliffs National Monument.  The sandstone has been worn smooth by water and wind erosion, but up close you can see how rough it is, like sandpaper.

The tiny sand grains are frosted by winds that blew them into dunes during the early Jurassic Period nearly 200 million years ago when this whole region of the American southwest was a vast desert similar to the Sahara of today.

The thin layers (laminae) of alternating color are at an angle to the main sandstone beds.  This is called cross-bedding and is characteristic of dune sands.  The wind blew in grains that had been stained brick-red by iron.  Then it turned around and blew in cleaner, lighter-colored grains from a different source.  These grains would cascade down the steeper lee side of dunes, creating the cross-beds.

The flatter, thicker layers have been eroded into steps, a characteristic of the Wave.  Because of variation in their hardness, their ability to resist erosion, the layers stand out or are recessed.  This differential erosion is caused by variation in the amount and hardness of cement binding the sand grains together.

So what this image shows on a micro-scale is an ancient sand dune in cross-section that is now being sculpted by present-day winds.  In other words, it shows winds in a desert of the distant past, when early dinosaurs roamed the area.  And it shows what the desert of today is doing to those ancient dunes

So an abstract image can tell you something real about the subject.  I believe that’s the best kind of abstract in fact.  I’m hoping the image shows what nature can do, not what me or my camera can do.  Please let me know whether or not I succeeded.  I hope your weekend was a lot of fun.  Thanks for reading.

Undulations

John Day Fossil Beds: To Clarno & Beyond   9 comments

Good day Central Oregon!

This is the last post in a series on the Painted Hills and John Day Fossil Beds in Oregon.  Be sure to check out the last two, which have tips for visiting the Painted Hills and Sheep Rock Units of John Day Fossil Beds National Monument.  It’s at Sheep Rock where we pick up the big counter-clockwise loop.

Just north of Cant Ranch on Hwy. 19 is a great hike.  Blue Basin is a fantastic section of blue-green sedimentary rock that rivals the Painted Hills.  It is the Turtle Cove member of the John Day Formation, some 30 million years old.  The blue-green color results from weathering of the volcanic ash in the rock to oxygen-poor iron oxide (green) and the clay celadonite (blue).

You can do a short in and out hike with interpretive panels, or a longer hike that takes you up and over the formations on a 3+ mile loop.  Make sure and take plenty of water, especially if it’s summer when this area can get very hot and dry.

Blue Basin with purple sage in bloom.

Blue Basin with purple sage in bloom.

Continuing north of Blue Basin, you’ll come upon an interesting geology stop.  A large lens of conglomerate is bisected by the road at Goose Rock.  The cobbles within the rock are perfect, like they had been plucked from a rocky stream.  But that stream flowed millions of years ago.  Continuing north you come to Cathedral Rock, which in the right light offers great photos with the John Day River as leading line.  Continue to the town of Kimberly, then follow the highway west along the John Day River to Service Creek, where lodging and camping is available.

Service Creek is a popular place for rafters and canoeists to put in for a float down the John Day.  In late spring, the river is perfect for this.  Rapids get up to class 3 but in general the river is quite mellow.  If you can handle a canoe through moving water, I recommend this over rafting, though both are a great idea.  It is an easy 2-night, 3-day float to the bridge crossing at Clarno.

Springtime brings green along creek bottoms in central Oregon.  Osage orange blooms on the right.

Springtime brings green along creek bottoms in central Oregon. Osage orange blooms on the right.

Keep on Hwy. 19 north through pine forests to the town of Fossil.  On the way, a detour can be made to the ghost town of Kinzua.  Two small forest service campgrounds are found along the route; they’re in pine trees not far south of Fossil.  Near these is Pioneer Park, which is perfect for a picnic.  A cold spring is one of its features, great for filling up with fresh clean water.  The creek running through is perfect for hunting crawfish.  If you have kids with you, this is a must stop for burning off some of that excess energy.

In the town of Fossil are two spots I recommend visiting.  One is the General Store, a very authentic old place that turns the pages back to a simpler time in America.  The other is the High School.  Why the High School?  Well, the hill next to it is one of the easiest places to find fossils I know of.  It’s an ancient lake bed that some 30 million years ago filled with sediments rich in volcanic ash.  Now perfectly preserved leaf fossils are revealed on dinner-plate rock surfaces.  The best part about it is you can dig your own fossils, and for a very small fee keep your favorites.  Recently established, the Oregon Paleo Lands Center here has a very helpful staff who will get you started and make sure your dig is successful.

A fossil leaf is perfectly preserved in lake-bed sediments rich in volcanic ash.

A fossil leaf is perfectly preserved in lake-bed sediments rich in volcanic ash.

From Fossil, take Hwy. 218 west toward Clarno.  Along the way an old homestead on the right makes a great photo stop.  When you begin to see tall cliffs on the right, you have arrived at the Clarno Unit of the National Monument.  There are a couple hikes here worth taking.  One, which takes off from a parking lot with bathroom, follows Indian Creek up to a shallow cave with pictographs.  This gives you a great feel for central Oregon’s ranching country.  Beautiful flowers bloom in April.

Another short hike takes off from the same parking lot, heading along the highway a short way before following a couple steep switchbacks up to the base of the cliffs.  You may see birds of prey hunting here.  The spectacular cliffs, called the Palisades, are made up of the Clarno Formation.  The Clarno, Eocene in age, is the oldest major formation in the Monument.  It is most famous for its fossils of huge mammals, along with one of the world’s premier fossil nut beds.  Very near here is an exposure of rocks where perfectly preserved nut fossils weather out like marbles.  It’s amazing:  some look as if you just reached into a bowl of walnuts – except they are heavier and made of stone.

A diorama depicting life in central Oregon when the area closely resembled modern Panama, but with early mammals prowling the forest, many now extinct.

A diorama depicting life in central Oregon when the area closely resembled modern Panama, but with early mammals prowling the forest, many now extinct.

A rare nearly complete skull of Eusmilus, a saber-toothed pre-cat of the John Day Fossil Beds.

A rare nearly complete skull of Eusmilus, a saber-toothed pre-cat of the John Day Fossil Beds.

If you want to visit the nut beds you can keep going on the trail up Indian Creek, but ask a ranger (back at Sheep Rock) for detailed directions.  There is also a fossil tree along the way that is upright and even includes traces of the roots!  But be aware that this area is shared by a science school.  In season (April – October) there are sessions taking place, with schoolkids getting a great field-based science education.  It’s best to give groups of kids and instructors their space and not attempt to hang out with them.

Following 218 west you cross the John Day River and climb over a pass to the tiny town of Antelope.  This was the base for a bizarre chapter in Oregon history.  In the 1980s a man from India, the Baghwan Shree Rashneesh, bought a ranch near here.  Having started his own religion, he brought a large group of followers and moved in.  The quiet ranching atmosphere was changed overnight, caravans of luxury cars and strangers running around.

It soon became clear that this was a cult.  The followers turned into a problem after several strange incidents and standoffs with local and state government officials.  It came to a head when they were caught poisoning the salad bar in a restaurant in the nearby town of The Dalles.  The Baghwan had also been dodging taxes.  The cult soon collapsed and broke up, and the Baghwan deported.  The ranch remains; I have toured the place and it is creepy-fascinating.  There is an old crematorium tilted over and rusting away in the sagebrush.  The followers included many talented engineers and other skilled people.  And they had not been idle.

Turning north at Antelope and staying on Hwy. 218 through a series of tight curves takes you up onto the plateau, to a ghost town named Shaniko.  Though a few people live here (which to me means it isn’t a ghost town), it is a shadow of once it once was.  You can get some good pictures wandering this little town.

Shaniko was once one of the busiest centers of sheep-ranching in the west.  This is the historic Shaniko Hotel.

Shaniko was once one of the busiest centers of sheep-ranching in the west. This is the historic Shaniko Hotel.

From Shaniko, if you follow Bakeoven Road, you come to the little community of Maupin, straddling the beautiful Deschutes River.  You can go white-water rafting or kayaking.  Continue west on Hwy. 216 back up out of the sagebrush and into the forests near Mount Hood.  You’ll hit Hwy. 26.  This is the fastest (and most scenic) way back to Portland.

I hope you enjoyed this little tour of central Oregon.  You may have heard that Bend is central Oregon, but it’s really not.  This large region, the John Day Basin, is both the geographic and cultural heart of central Oregon.  It is much more than the Painted Hills.  If you want to explore a fascinating and non-touristy part of the west, a region with great photo opportunities and interesting human and geologic history, you can’t do much better.

South-central_Oregon_5-23-12_5D_005

John Day Fossil Beds & Climate Change   4 comments

An old dairy farm along Bridge Creek in eastern Oregon near the town of Mitchell, it appears to have once been a going concern.

An old dairy farm near the town of Mitchell, Oregon appears to have once been a going concern.

As mentioned in my last post on the Painted Hills, this area of Oregon is about so much more than some colorful formations.  A little preview at the end of that post last Friday was a short description of the old dairy farm near Mitchell (see above).  And it’s from there that we’ll continue our road trip through John Day Fossil Beds National Monument in Oregon.

Travel east from Mitchell on Hwy. 26 toward the monument headquarters at Sheep Rock.  You will first come to Picture Gorge, a spectacular cut through stacks of basaltic lavas.  The Picture Gorge Basalt is a southern outlier of the great Columbia River Basalt flows to the north.  The gorge is named for ancient Native American rock art found on the walls.

Since I can't find any very good images of Oregon rock art, here is a pictograph from Chaco Canyon in New Mexico.

Since I can’t find any very good images of Oregon rock art, here is a pictograph from Chaco Canyon in New Mexico.

To see and photograph some pictographs, drive to the east end of the gorge and park alongside the John Day River.  Look up to the walls across the road.  From here, if the river is low enough, you can get a much closer look at great rock art alongside the river.  Just drop below the road and walk a hundred yards or so upriver, looking for short, smooth walls to your right.  A rare pictograph of a salamander can be found.

Midway through Picture Gorge you’ll turn north on Hwy, 19 and drive a short distance to the Sheep Rock Unit.  There is a great museum that explains the areas rich fossil heritage.  This is an important region of the world for paleontologists.  Along with Wyoming’s Green River area, it is where well preserved fossils of ancient mammals, plants and other creatures can be found.  These remains, preserved within colorful sedimentary rocks shed off  ancient volcanoes that were eroded away long ago, document the explosion of mammalian diversity in the Eocene (56-34 million years ago).

The typical bloom you find near water in eastern Oregon is monkeyflower.

The typical bloom you find near water in eastern Oregon is monkeyflower.

Mammals started off very small, literally in the shadow of dinosaurs.  Once the dinosaurs went extinct 65 million years ago, mammals slowly evolved and diversified until an inevitable point.  Just as happened with dinosaurs near the peak of their diversity, mammals began to evolve into huge forms.  This is well documented in the John Day.  In fact, the region has abundant mammal fossils all the way up through the Miocene (23-5 million years ago).

One of the largest mammals of all time was the huge rhino-like brontothere.  Enormous ground sloths roamed here as well.  Other mammals of the John Day:  early horses the size of dogs, camels, a large variety of canids, cats (including early saber-toothed varieties), rodents, even early primates.  And it’s not just mammals:  huge fossil turtle shells are found.

A very important part of the John Day fossil beds is the amazing variety of plant fossils.  This allows the environments in which these animals once lived to be worked out in detail.  A period of global warming is documented here, followed by a long slow cooling and drying trend that has continued to the present day.  Nowadays of course humans are busy driving the climate in the opposite direction, toward a climate last experienced by those now-extinct mammals of ancient North America.

The old homestead  Cant Ranch, with Sheep Rock in the background.  Click on image if interested in it.

The old homestead Cant Ranch, with Sheep Rock in the background. Click on image if interested in it.

An Aside:  Climate Change – The Debate?

I recall having a group of high school science students at the museum at Sheep Rock.  I was showing them the fossils and how they told us the ancient climate was lush and subtropical.  On the wall was a chart that showed the estimated CO2 levels in the atmosphere during that period, and how they coincided with the types of plant and animal fossils.  A man and his wife were listening off to the side.

Later I heard him telling his wife, “see, what did I tell you?  Global warming happened in the past and was natural.  We don’t have anything to do with it, even if it was actually happening.”  Or words to that effect.  I wanted to correct his misinterpretation of the meaning of the evidence but realized it was not a good idea for several reasons.  For one thing, a person who uses faulty logic certainly missed something early in their upbringing/education.  When they got older they internalized this way of thinking, so that any faulty interpretations they make are perceived to be merely “common sense”.  Very difficult to explain anything to such a person.

Though it’s true that a warm, tropical climate is very conducive to a diversity of life, it is the change to those conditions that poses the risk.  And that’s especially true for very rapid changes like the one we’re entering now.  A transition to an ice-free world is upon us, and we can only pray that it will only be accompanied by a drowning of our coastal cities and dramatic changes to agriculture and water supplies.  The worse-case scenarios are much more dire.

Scientists are much too conservative to talk about these darker scenarios with the press.  But trust me, they aren’t pretty.  Picture enormous clouds of poison hydrogen sulfide gas spewing out of stagnant oceans, killing everything that breathes unless it is hidden underground.  There is evidence that this happened during past mass extinctions.

Old homestead in central Oregon.

Old homestead in central Oregon.

Leaving aside all these sunny thoughts, it’s amazing to think this semi-arid region of grassland looked like present-day Panama in the early Eocene (about 50 million years ago).  It had active volcanoes and the coastline was closer.  With no Cascade Mountains, there was no rain-shadow effect.  The warm Pacific Ocean sent abundant moisture over a lush river-laced landscape dotted with volcanoes.  Many of the animals (e.g. camel, rhino & elephant) that during present times are found only in Asia or Africa roamed (in early form) the jungly American wetlands of the west.

Animals like horses and camels evolved here in North America, then migrated across the Bering Land Bridge to Asia and eventually Africa.  They went extinct here.  Many other now-extinct animals, like brontotheres, oredonts (large & pig-like), creodonts (looked like a cross between a hyena and cat but more heavily built) and nimravids (a sleek & agile saber-toothed pre-cat) all lived, died and eventually went extinct here.

A mural depicting life in Eocene Oregon.

A museum mural depicting life in Eocene Oregon.

I’ve spent quite a bit of time out here teaching science.  After a time, I got to where I could experience that ‘other’ Oregon.  Believe it or not, for paleontologists or anyone who sees enough fossils, absorbs enough knowledge, and then quiets themselves while out in the places where the fossils are found, it is possible to time-travel with your mind.  You can bring up vivid images of that other world in the silence that surrounds you during semi-meditative states.  You actually start to feel the humidity and hear the buzzing of tropical insects.  Very cool.

So check out that museum!  Right across the road lies the historic Cant Ranch and picturesque Sheep Rock.  This is a great place for photos, with the old barns, the John Day River and Sheep Rock begging to be part of your compositions.  The rangers run tours of the historic ranch, giving you a picture of the old homesteading days when the west was first being settled by whites and their livestock.

The last part of this series covers the northern part of our loop, including the Clarno Unit of John Day Fossil Beds National Monument.  Thanks for reading!

Sunset, John Day River Valley, central Oregon.

The San Juan Mountains   11 comments

An alpine lake high in the San Juan Mountains, Colorado.

An alpine lake high in the San Juan Mountains of Colorado.

The San Juan Mountains are my favorite mountain range in Colorado.  They are not the highest mountains in the state, though with six peaks surpassing 14,000 feet (4270 meters) in elevation they’re close.  It is the largest range in Colorado by area.  They slice spectacularly through the southwestern part of the state, forming a stunning Rocky Mountain landscape.

The major towns bordering the San Juans are Durango, Montrose and Alamosa.  Telluride, Creede and Silverton are smaller towns with historic, touristic and recreational personalities.  Hiking, mountain climbing & biking, horse-riding and white-water rafting are very popular, as are 4WD jeep rides.  There are four ski areas in the range, with Telluride being by far the biggest and most famous.  There are a plethora of summer homes and ranches, many owned by wealthy people.  Some are even famous (Tom Cruise is one).

The rugged San Juans in SW Colorado.

The rugged San Juans in SW Colorado.

William Henry Jackson, a photographer’s photographer

An intrepid photographer named William Henry Jackson, whom many of you might already know about, trekked through this range on his mission to document the best of the rugged American West in the late 1800s.  As part of the Hayden Expedition, he used pack animals and his own strong back to lug his large-format camera (complete with huge glass plates) up and down these steep mountains.

He set up make-shift tents that served as darkrooms, developing his prints often on the very summits of the mountains.  All in all he made about 300,000 black and white pictures.  These images, reproduced in newspapers in cities worldwide, played a large part in forming an idyllic image of the American West in the minds of those looking for new opportunity.  The call of “Go West young man!” now had superb pictures to go with it, and the mass migration soon followed!

Ranch land at the foot of the San Juan Mountains.

Ranch land at the foot of the San Juan Mountains.

 

Geology

The San Juans are a large western branch the Rocky Mountains.  Like the rest of the chain, they formed by the uplift and buckling of a large pile of older sedimentary and volcanic rocks during the late Cretaceous (the dinosaurs went extinct at the end of the Cretaceous, 65 million years ago).  This massive crustal “squish” happened because of a collision between two huge chunks of Earth’s crust: the Pacific and North American Plates.

Some of the highest and most rugged peaks in the San Juans are made of very hard igneous intrusions (granite is an example) that resist erosion.  These so-called plutons were intruded as the mountain building process got going.  Many of the flat-lying layers of sedimentary rocks forming the canyon walls of the adjacent Colorado Plateau lap up onto the San Juans.  There they take on a different look, being strongly deformed by folding and faulting.

Ouray, Colorado is a small town situated in a spectacular spot.

Ouray, Colorado is a small town situated in a spectacular spot.

Hard sedimentary rocks like quartzite, which is metamorphosed (heated and changed) sandstone, form prominent peaks and cliffs because quartzite is hard like the plutonic intrusions.  Other sedimentary rocks, such as the mudstones and sandstones of the dinosaur fossil-bearing Morrison Formation, typically form the rubbly slopes bordering the peaks.  Many valleys and canyons follow faults.  Ouray, Colorado lies at the base of a steep grade because of the E-W trending Ouray Fault.

Volcanism is one other important force that helped to form the San Juan Mountains.  Large and explosive volcanoes erupted in middle Tertiary times (about 30 million years ago).  Many calderas, including the Silverton Caldera, make up what’s called the San Juan Volcanic Field.  Calderas are bigger than craters and are formed when the volcano violently explodes and collapses back into its emptied magma chamber.

You can see these volcanics (tuffs – rock from volcanic ash and lavas) by driving up and over spectacular Red Mountain Pass.  In the San Juans, the colorful volcanic rock forms high but more rounded peaks that are less rugged than those formed by earlier igneous intrusions of the main mountain-building event.

Aspens take on a very different look after they lose their leaves in late autumn.

Aspens take on a very different look after they lose their leaves in late autumn.

Thar’s Gold in them thar hills!

In the late Tertiary, from about 20 to 10 million years ago, the slowly cooling granitic intrusions that were the sources for those explosive volcanoes sent forth gold and silver-bearing fluids into the faults and fractures of the calderas.  So like so many mountainous regions of the world, the events that formed valuable mineral deposits were the penultimate phases of the mountain-building process, the last gasp of the big granite bodies solidifying deep underground.

In southwest Colorado as in similar places throughout the world, these events dictated the much later human history of the area.  The mining history of this area, while interesting, also has a dark side.  The Summitville Mine in the eastern San Juans was worked by the old-timers in the late 1800s, well before modern environmental regulations.

The pollution from acid drainage resulted in the Environmental Protection Agency (EPA) declaring the area a Superfund site.  They have been trying to clean it up since the 1990s.  The EPA wanted to list an area near Silverton for Superfund status, but local opposition forced them to drop the idea and rely on the mining company to help control acid drainage.  The local economy relies heavily on tourism, and residents did not want that reputation tainted.

Silverton sits in a high valley between Molas and Red Mountain Passes.

Silverton sits in a high valley between Molas and Red Mountain Passes.

Silverton's mining-driven boomtime was in the late 1800s, as the architecture suggests.

Silverton’s mining-driven boom-time was in the late 1800s, as the architecture suggests.

 

The San Juan Mountains, a real Rocky Mountain wonderland, make for outstanding landscape photography.  In early summer there are spectacular wildflower displays. In autumn the aspens turn gold beneath the snow-dusted peaks.  If you have never been to this part of Colorado, I recommend making every effort to visit sometime soon.  And don’t forget your camera!

Click on any of the images to go to my image galleries.  They are all copyrighted, so aren’t available for free download without my permission.  If you’re interested in purchase of fine-art prints or high-resolution downloads please contact me.  Thanks for reading and have a great day!

The setting sun's light brightens the peaks of the San Juan Mountains,  Colorado.

The setting sun’s light brightens the peaks of the San Juan Mountains, Colorado.

The Alvord Desert, Oregon   7 comments

The Trout Creek Mountains in southeastern Oregon bask in last rays and the desert prepares for night.

The Trout Creek Mountains in southeastern Oregon bask in last rays as the desert prepares for night.

When I need some wide-open space, I come to this corner of Oregon that we call the state’s “outback”.  I drove through on my way to the Rockies recently and revisited a few old haunts.  But this was the first time I had actually camped on the playa of the Alvord Desert.  While this region is indeed technically a desert (averaging 7 inches/yr. precipitation), I’m not sure why they chose to call this particular place the Alvord Desert.

The Alvord part is predictable, named after a general from the East, from the Civil War no less.  But the desert part is curious.  The whole region is classified as a cold semi-arid desert.  It’s dry and it’s high (4000 feet/1220 meters).  But the area named the Alvord Desert is actually a large playa, a dry lake bed.  So why not call it the Alvord Playa?

Venus sets & the stars come out as night comes to the Alvord Desert in SE Oregon.

Venus sets & the stars come out as night comes to the Alvord Desert in SE Oregon.

Early morning reveals the Pueblo Mountains to have been dusted by snow overnight.

Early morning reveals the Pueblo Mountains to have been dusted by snow overnight.

Climate & Geology

The region’s aridity is caused by the rain shadow of the Cascades and other mountain ranges.  The Alvord itself is in the very dramatic rain shadow of Steen’s Mountain, which rises directly west.  (The Steen’s is also a very spectacular destination in it’s own right.)  The Alvord is a spectacular example of a playa, so dry and flat in summer and fall that you can easily drive and land a plane on it.  In fact, it’s been used to set land speed records, like the Bonneville Salt Flats down in Utah.

The salty playas of this region of North America form because erosion from surrounding mountains dumps fine sediment into the bottom of the basin and the shallow water that collects there cannot run out.  (This isn’t called the Great Basin for nothing.) The water evaporates, leaving behind salt flats and quickly drying muds.

The playa of the Alvord Desert in Oregon attracts a group of "wind-riders".

The playa of the Alvord Desert in Oregon attracts a group of “wind-riders”.

Even a light wind can propel these guys at quick speeds across the Alvord.  I can't imagine the speeds in heavy wind.

Even a light wind can propel these guys at quick speeds across the Alvord. I can’t imagine the speeds in heavy wind!

The Alvord lies near the northern extent of the the Basin and Range province, a term geologists prefer over Great Basin.  Extending down through Nevada and eastern California, and over into western Utah, it is a series of linear mountain ranges and adjacent basins formed by block faulting.  Huge sections of the earth’s crust rise up while on the other side of the fault the adjacent basins drop down.  It happens this way because the crust just below is being stretched and rifted apart, much like the Great Rift Valley in Africa. Since this shallower part of the crust is brittle, faults form.  Earthquakes along these faults still happen, so it is an ongoing process.

Fall-flowering shrubs dot the "pediment", the transition from basin to range, in this case from the Alvord playa to Steen's Mountain.

Fall-flowering shrubs dot the “pediment”, the transition from basin to range, in this case from the Alvord playa to Steen’s Mountain.

Reasons to Visit

I hope you get to visit this region one day.  Other than the glorious skies and wide-open spaces, it has a lot to offer.  It is a fantastic place for bird-watching in springtime (March/April).  Just northwest of the Alvord are huge & temporary, shallow lakes, which attract large flocks of migrating birds.  The area around Steen’s Mountain is home to Kiger mustangs, wild horses that are known far and wide for their spirit and strength. You’ll probably hear coyotes every night you camp.  And you might see a few buckaroos working cattle from horseback, as has been done here ever since white settlement in the 19th century.  The area is dotted with the remnants of old homesteads and ranches.

Hope you have a great week.  Thanks for reading!

View out onto the Alvord Desert at dusk, where recent rains have left small pools and channels of water.

View out onto the Alvord Desert at dusk, where small pools and channels of water from an early fall storm try to make their way out onto the playa.

The Trout Creek Mountains lie just south of the Alvord Desert near Oregon's border with Nevada.

The Trout Creek Mountains lie just south of the Alvord Desert near Oregon’s border with Nevada.

The Cascades III: Mount Rainier, Part 1   8 comments

Mount Rainier is reflected in a small tarn in the subalpine meadows called Indian Henry's Hunting Ground.

Mount Rainier is reflected in a small tarn in the subalpine meadows called Indian Henry’s Hunting Ground.

It’s no use stalling anymore.  Let’s continue my series on the Cascade Mountains of the Pacific Northwest.  Check out Part I, an introduction to the Range’s geography & geology.  So which mountain should be next?  Well, there are many interesting options.  There are the little-known “climber’s” peaks of Mount Jefferson and North Sister, Glacier Peak and Mount Stuart.  There are the popular recreation meccas of Mounts Baker, Bachelor and Hood.  But there is just one mountain I can’t put on hold any longer: the Big Kahuna, the sleeping giant, the Mother of Waters, training ground for Everest, Seattle’s sky-ornament, Tahoma, Mount Rainier.

The images you see here are copyrighted and not available for free download without my permission, sorry about that.  If you want to see purchase information, just click on the images you’re interested in.  If you have any questions, please contact me.  Thanks for your interest!

Mount Rainier and the largest glacier in the lower 48 United States, the Emmons, are bathed in early morning sunshine.

Mount Rainier and the largest glacier in the lower 48 United States, the Emmons, are bathed in early morning sunshine.

Mt. Rainier, at 14,411 feet (4392 meters), is one of America’s most spectacular mountains.  It sticks up hugely and dramatically a little more than 50 miles southeast of Seattle, Washington.  Rainier’s prominence is enhanced by a total of 26 glaciers with over 35 square miles of ice.  In North America, only Alaska and the Canadian Rockies have more dramatic, glaciated mountains.  By the way, don’t get confused about Part III and Part 1.  It’s just that with this particular mountain, there’s too much to fit into one post.  Stay tuned for one or two more posts on Rainier, but we’ll still be on the Cascades Part III until we jump to another mountain.

Mount Rainier's Paradise Park

Mount Rainier’s Paradise Park

The hairy pasqueflower blooms in contrast with indian paintbrush.

The hairy pasqueflower blooms in contrast with indian paintbrush.

Mount Rainier was named by Captain Vancouver of England for a friend of his, Rear Admiral Rainier.  It’s original name, from a local American Indian tribe the Puyallup is Tahoma (or Tacoma).

A Dangerous Volcano

Rainier is considered one of the world’s most dangerous volcanoes, and there are a few important reasons for this. Like Vesuvius in Italy, Rainier is situated quite close to population centers.  That is the most important factor that makes it dangerous.  The second most important reason is not, as you’d expect, the volcano’s activity level.  Rainier sleeps for long periods.  Instead, what makes it potentially deadly is the fact that it is steep and weak.  In other words, the same thing that makes it dramatic, sticking up so steeply as it does, also makes it dangerous.

Spray Falls on Rainier's northwest side is a spectacular cascade.

Spray Falls on Rainier’s northwest side is a spectacular cascade.  The mountain receives abundant precipitation, much of it in the form of snow.

The glaciers, with their incredible erosive power, have done a very good job of steepening the volcano.  But how is it weakened?  As the mountain sleeps between eruptions, it sits above the magma chamber below and literally stews in its own juices. Rainier is in a wet climate, and the mountain’s bulk draws even more precipitation its way.  Because of this, Rainier’s rocks are wet.  Add heat and acidic gases from below and you have a corrosive mix.  As a result the rocks are altered to clays, greatly weakening Rainier’s steep cone over time.  In other words, much of the peak is literally rotten.  Add these two things together, the volcano’s steepness and its inherent weakness, and you have a very real and constant hazard on your hands.

Fields of lupine bloom in the subalpine meadows of Mount Rainier, Washington.

Fields of lupine bloom in the subalpine meadows of Mount Rainier, Washington.

The biggest volcanic hazard at Rainier is not from lava flows but from mudflows (aka lahars).  If the mountain erupts lava or hot ash, large amounts of ice could melt quickly, causing a catastrophic flow of mud, rocks, trees, bridges, cars, etc. that cascades down river valleys, wiping out everything in its path.  But here’s the thing: an eruption is not really necessary to bring destruction to the surrounding populated valleys.

Now imagine a small earthquake, perhaps during an unusually warm summer when much of the ice high on the mountain is melting (can you say global warming?).  This could easily trigger a large and very destructive mudflow.  Geologists know this has happened in the past.  In fact, a good portion of the city of Tacoma (plus some of Seattle) is built on deposits from an enormous Rainier mudflow that buried the area some 5000 years ago.

Bears are not that uncommon at Mount Rainier.

Bears are not that uncommon at Mount Rainier.

The Rainier region now has a warning system made up of sirens that are triggered when mudflows higher on the mountain begin.  Citizens of towns like Orting and Enumclaw are taught to heed these sirens by escaping to high ground.  Mudflows are powerful enough to sweep away large bridges and buildings like a spoiled toddler kicks over his leggos.  But all their dirty work is limited to river bottoms, so getting up out of the valley will save your life.

The last of the day's light falls on Mount Rainier in Washington.

The last of the day’s light falls on Mount Rainier in Washington.

Carefree at Coldwater Lake   18 comments

A nature trail at Mount St. Helens' Coldwater Lake uses an elevated boardwalk to give visitors a great view.  There is also a hiking trail along one lake shore.

A nature trail at Mount St. Helens’ Coldwater Lake uses an elevated boardwalk to give visitors a great view. There is also a hiking trail along one lake shore.

Summer is going by as quick as it can, and carefree moments are precious now.  Last weekend on the way back from the Olympic Peninsula I made one of my patented “left turns” (why is always a left?) and on a whim headed up to Mount St. Helens.  The weather promised some nice light and I wanted to get some good shots of the mountain.  The following morning was beautifully misty, sunset was gorgeous, and the flowers were surprisingly still blooming fresh.  But the moment I will take from the trip was one that happened without a camera around my neck.

Coldwater Lake at Mount St. Helens, Washington.

Coldwater Lake at Mount St. Helens, Washington.

After hiking up near the crater mouth, I headed back down to Coldwater Lake.  This is a beautiful big lake that was formed during the famous eruption in 1980.  The massive landslide that triggered the eruption (that in turn destroyed much of the forest in these parts) also dammed Coldwater Creek.  And just like that nature’s fury left a jewel in its wake.  When I arrived after the hot, dry hike, I immediately thought SWIM!  I was in such a hurry that I left the camera behind and jogged partway up the sunny shore, looking for a likely spot.  I found a perfect spot where a large tree, weathered silver and smooth, lay partway out into the lake, forming a sort of natural dock.  These massive old-growth trees lay all about the area, testament to the eruption’s power.

The outlet of Coldwater Lake winds its beautiful way through the now-vegetated landslide debris from the 1980 eruption.

Some of the many logs scattered along the shores of Coldwater Lake, remnants of the once dense forest of tall evergreens that grew here before the 1980 eruption.

I couldn’t believe how perfect the water was when I dove in.  It was by no means warm, but it wasn’t too cold either.  Refreshing!  After the swim I just lay on the big log staring up into the sky.  All I could hear was a nearby kingfisher and without trying the clouds started making recognizable shapes.  How many summer days during childhood did I do this?  And why have I not done much of it since?  The sun dried me and I dozed in and out.  All my cares melted away.

The outlet of Coldwater Lake winds its beautiful way through the now-vegetated landslide debris from the 1980 eruption.

The outlet of Coldwater Lake winds its beautiful way through the now-vegetated landslide debris from the 1980 eruption.

After the swim I was ready to shoot some pictures.  I think the summery hour or so I had just spent made the picture-taking that much better.  I was refreshed and calm, the perfect way to be when doing anything, especially something creative.  It’s a reminder that those carefree summer moments (whether they are in summer or not) have a very useful purpose.  Without them we cannot do our best work.  To everyone out there, before summer ends: put your devices away, have nothing in your pockets, and just go be a kid again for awhile.  Have no real purpose.  Let the summer breezes and sounds clear your mind.  Be carefree for once.  You will thank yourself later, believe me.

For sunset I went to a nearby viewpoint that shows the huge area of landslide debris from the 1980 eruption that filled the North Fork Toutle River Valley.  This created Coldwater Lake, which is just out of view to the left.

For sunset I went to a nearby viewpoint that shows the huge area of landslide debris from the 1980 eruption that filled the North Fork Toutle River Valley. This created Coldwater Lake, which is just out of view to the left.

The Cascades I: Volcanoes Give and Take Away   16 comments

Sunrise on the north side of Mt Hood from the pastoral Hood River Valley, Oregon.

Sunrise on the north side of Mt Hood from the pastoral Hood River Valley, Oregon.

This is the mountain range I’m most familiar with, my home range.  I’ve climbed all of the high Oregon Cascades and many of the bigger Washington ones as well.  So I have personal experience and knowledge of these peaks.  Named for the many waterfalls that tumble over their volcanic cliffs, the Cascades are essentially a northern analogue of the Andes in South America.

The waterfalls for which the Cascades are named occur all through the range, including here at Toketee Falls.

The waterfalls for which the Cascades are named  include Toketee Falls.

GEOGRAPHY

The Cascades are volcanoes that still erupt from time to time, but with the exception of a single mountain are not the most active volcanic chain in the world by any means.  More on the exception below.  The Cascade Range, which stretches for 700 miles (1100 km.) in a north-south direction from Mount Garibaldi in Canada to Mount Lassen in California, is part of the Pacific Ring of Fire (see below).  This whole region of the western Pacific Northwest is often called Cascadia.

The Cascades are dotted with beautiful mountain lakes.

The Cascades are dotted with beautiful mountain lakes.

The dramatic and beautiful mountains that make up the Cascades in most cases exceed 10,000 feet (3000 meters).  The high peaks are generally well-spaced, with many miles of forested lower mountains and hills between each snow-capped peak.  Oregon’s Three Sisters area (which actually includes 5 big volcanoes) is an exception to this wide spacing.  The bunched-up and much more rugged North Cascades in Washington are a whole different range geologically, one that happens to coincide in space (but not time) with the volcanoes of the Cascades.

A wet meadow in Crater Lake National Park blooms with pink monkeyflower, among other flowers.

A wet meadow in Crater Lake National Park blooms with pink monkeyflower, among other flowers.

GEOLOGY

The highest peaks in the Cascades are quite young, most less than 100,000 years old – a moment in the earth’s 4.5 billion-year history.  They are built upon a much older eroded volcanic range, arranged along an axis situated slightly to the west of the present locus of volcanic activity.  These older volcanoes began erupting some 37 million years ago.  It’s lucky for life (including us) that these older, heavily eroded volcanoes are around.  It’s the reason we have those lush forests, those cold streams that nourish the region’s great fish runs, and the habitat for the region’s other wildlife.  And let’s not forget the many waterfalls!

From high on Cooper Spur at Mount Hood, Oregon, the view north includes Mount Adams in Washington.

From high on Cooper Spur at Mount Hood, Oregon, the view north includes Mount Adams in Washington.

The older ancestral Cascades are also responsible for the region’s enormous timber resources plus the very rich soils that drew settlers west along the Oregon Trail.  Volcanoes combine with ample rainfall to make rich soil for farming.  By the way, many often wonder why so many people, worldwide, live near dangerous volcanoes.  It’s simple:  the rich soils around volcanoes, the productive farmland.  There is really not much choice.  We must eat, and so we must live near volcanoes.

While the Western Cascades are responsible for many of the Northwest’s assets, let’s not totally dismiss the younger High Cascades.  Their snowpack, lasting well into summer, gives farmers and ranchers (especially those to the east) water for their crops through typically dry summers.

The older western Cascades are very different in character than the high Cascades.

The older western Cascades are very different in character than the high Cascades.

The Cascades are stratovolcanoes (aka composite cones).  These are the steep-sided, conical volcanoes you drew as a kid in school.  They are made of alternating layers of lava-rock and pyroclastic (ash) deposits.  The volcanic rock is characteristically lighter colored than the basalt which covers the region to the east of the Cascades.  A typical volcanic rock for the Cascades is andesite (named for the Andes), which flows over the ground in a somewhat stickier manner than more fluid basalt (Hawaiian volcanoes erupt basalt).  The Cascades do have their share of basalt too, along with dacite and a few other types of volcanic rock.

An uncommon volcanic rock of the Cascades is obsidian.  It is very rich in silica (SiO2), which is also what quartz is made of.  In liquid lava, dissolved silica acts to make it stickier, more viscous.  Water does the opposite, makes lava less viscous – more fluid.  Obsidian is so rich in silica and erupts so dry that it literally squeezes out of the ground like thick toothpaste, heaping up into mounds and ridges.  Once cooled, obsidian is a beautiful natural glass, normally black, that can be sharp enough to serve as surgical instruments.  Obsidian arrowheads left along old American Indian trails and hunting grounds can still be found throughout the Northwest.

Admiring the view while on a climb in the Cascades.  That is Mount Adams in Washington.

Admiring the view while on a climb in the Cascades. That is Mount Adams in Washington.

THE RING OF FIRE AND PLATE TECTONICS

The Pacific Ring of Fire is that huge circle of volcanoes and earthquake activity that circles the Pacific ocean basin.  Some of the world’s most spectacular eruptions and devastating earthquakes happen along the Ring of Fire.  Truly an enormous geologic feature, it exists because the earth’s tectonic plates rub against and collide with each other (see addendum below if you don’t know about plate tectonics already).  Although they act slowly, the forces are gargantuan.  And something has to occasionally give.

The big snow-capped peaks of the Cascades are classic strato-volcanoes.

The big snow-capped peaks of the Cascades are classic strato-volcanoes.

One example of the power and beauty of the Ring of Fire lies in the remote Aleutian Islands and Russia’s Kamchatka Peninsula.  Here the huge Pacific Plate dives under the North American continental plate (plus a smaller one called the Okhotsk Plate) along a so-called subduction zone.  The plate partially melts as it descends, because of the heat of course – but also because of it is loaded with water (which acts as a flux).  Plumes of magma rising from the descending and melting plate eventually erupt into some of the world’s most active (and thankfully remote) volcanoes.  In the Southern Hemisphere on the opposite side of the Ring of Fire, the oceanic Nazca Plate subducts under the South American plate to form the longest volcanic range in the world, the Andes.

Crater Lake in Oregon fills the collapsed caldera of Mount Mazama, which blew its top about 7000 years ago.

Crater Lake in Oregon fills the collapsed caldera of Mount Mazama, which blew its top about 7000 years ago.

All throughout the Ring of Fire there are earthquakes.  Some of the largest happen as a result of subduction and are called megathrust quakes (how’s that for a name!).  The earthquake that caused the destructive Japanese tsunami of 2011 was of the  megathrust variety.  This enormous earthquake happened where the Pacific Plate subducts beneath Japan’s Honshu Island.  The Pacific Plate moved as much as 20 meters (66 feet) west during the minutes-long quake.  Honshu drew closer to America by about 2.5 meters (8 feet).  The equally destructive Indian Ocean tsunami of 2004 was also generated by a megathrust quake along a subduction zone.

Other earthquakes happen when two tectonic plates slide past each other.  The San Andreas in California is the most famous example of this so-called transform boundary.  Because these earthquakes happen on land and have fairly shallow epicenters, they can be very destructive.  This is despite the quakes being generally smaller than subduction-zone, megathrust earthquakes.

Climbing in the Cascades.  Mount Adams (right) and Rainier are visible.

Climbing in the Cascades. Mount Adams (right) and Rainier are visible.

ADDENDUM: PLATE TECTONICS

The crust of the earth (plus some extra beneath it) is broken into enormous semi-rigid plates.  Over time, the plates move across the planet’s surface, on average about as fast as your fingernails grow.  That’s an average; during big quakes they can move up to a hundred feet!  But overall it’s a very slow process.  It can take over a million years for a plate to move 50 miles.  They ride atop enormous convection currents in the semi-molten part of the upper mantle.  The mantle is that layer that lies directly beneath the earth’s crust.  The weight of tectonic plates as they descend into the mantle along subduction zones (like the one that lies just off the Pacific Northwest coast) helps to pull the oceanic plates along.

Why do we have tectonics while the other planets don’t seem to?  For one thing the energy that drives the convection currents comes from heat given off by the still cooling interior of the earth.   Mars is too small to have much heat left.  For Earth, much of the core is still molten, and our fast spin sets up complex circulation patterns (which cause our magnetic field).  Combined with heat from the decay of radioactive elements, this gives rise to huge, slowly rising zones of heat.  When they hit the colder, more rigid upper parts of the earth, the crust, the currents spread outward horizontally.

Silver Star Mountain in Washington, after a heavy snowfall.

Silver Star Mountain in Washington, after a heavy snowfall.

But there’s another reason for plate tectonics.  It is because we are a water planet that all this partly molten rock is around.  Venus is much too dry for plate tectonics to get going.  Without water the pressures deep below would not allow enough melting.  Water essentially lubricates the earth’s tectonic system.  And without plate tectonics complex life would most likely not be possible, yet another way water is crucial to a living earth.

This series will continue.  If you are interested in any of the images, just click on them.  They are copyrighted and not available for download without my permission.  Please contact me if you have any questions.  Thanks for reading!

Sunset over the Western Cascades, as viewed from Mount Hood in Oregon.

Sunset over the Western Cascades, as viewed from Mount Hood in Oregon.

%d bloggers like this: