This is the last of three posts on the geology and ecology of Death Valley National Park in California. I hope you’ve enjoyed them. Remember for my images, click on them to be taken to the website, where purchase for download or prints (framed or unframed) is very simple. These photos will be up in their full-sized glory soon, but if you are interested now, please contact me. These versions are too small to do anything with, so please enjoy them without attempting to download from the blog. Thanks.
Death Valley was influenced by the Pleistocene Ice Ages that started a couple million years ago and ended about 10,000 years ago. No, glaciers did not descend into the valley; it never got that cold. But the large ice sheets to the north led to a much wetter climate throughout most of the ice-free parts of the continent. So as you might imagine, large basins like Death Valley filled with large lakes. At one time there were lakes hundreds of miles long. The one that occupied Death Valley is called Lake Manly, at one time 80 miles long. Where did the water go? Underground of course. You see the top of this great aquifer at Badwater, and in wet years (2004) a shallow lake reappears atop the normally dry salt flats.
The Great Salt Lake in Utah is the largest remnant of the paradise for water birds that the West was during the Ice Age. This world of wetlands supported a healthy early Native American population. As the lakes shrank and dried up some 10,000 years ago, the native groups migrated north and east, the evaporite minerals accumulated in great quantities, and desert pup fish evolved.
Can fish be cute? Sure they can! The cute little pup fish that make Death Valley their home are small remnants of once-huge schools that swam the huge lakes of Ice Age times. If you know about the great Rift Valley lakes of Africa (Tanganyika, Malawi, etc.), you might know of the beautiful little aquarium fish that make those lakes their homes. The same was true in North America during the wetter times of the Ice Age. When the lakes dried up and separated into smaller, shallower and saltier bodies of water, those fish were forced to adapt to progressively warmer and saltier water.
This is exactly the sort of crisis that drives accelerated rates of evolution. It’s a changing environment that separates breeding populations into smaller and smaller parts that most easily leads to very specialized life forms, adapted to a specific environment. In the case of the pup fish, this story has reached an extreme point in modern times at Devil’s Hole, a separate section of the National Park located not far east in Nevada. Here live one of the world’s rarest species, the Devil’s Hole pup fish. These small fish hide in the deep crevices of an extensive spring system. The water, a remnant itself of a much bigger body, is incredibly salty.
Pup fish are super-specialized creatures, a testament to how difficult it is for nature to kill off one of its own. They can withstand high salt concentrations and very warm water. They are most likely doomed, however, as the climate of the American West continues to become warmer and more arid. But they will continue their fight so long as we don’t do something stupid like pump nearby groundwater dry.
I hope this little tour of one of my favorite playgrounds has made you want to visit, has given you a good knowledge background, and spurred you to do some additional research. There is plenty of good information on the Web, and not all of it on Wikipedia! I also hope this has given you an appreciation for how the geology of a region influences almost everything else about it. It’s even true where you live!
I apologize for not writing quite so much on desert ecology. Hmm…maybe I should do just one more post!