Alluvial Fans

An alluvial fan is semicircular in shape, and is comprised of deposits of rocks and other debris that were shed from the mountains on to the valley floor. In Death Valley, alluvial fans can be found where canyons drain from the mountains to the valley floor. Death Valley is a great place to look at alluvial fans because they are still undisturbed. In other places, like the foot of the San Gabriel Mountains, people have built homes on top of them. These residents have sometimes found themselves at the mercy of the powerful forces which create alluvial fans.

Glazner explains what creates these features: "Alluvial fans are produced by debris flows, which are very nasty flows of mud, boulders, and water that come down these canyons during very heavy rainfall. So a debris flow might come down a given canyon once every decade or so. They're very infrequent events. But during extremely heavy rains, material gets loosened up and flows down very steep canyons and mountains, such as the Black Mountains, and pours out of the mouth of the canyon and spreads out when it hits the valley floor into a nice cone shape. If you look at these alluvial fans, you'll see they have very coarse debris at the top because the biggest boulders get dumped up there and the debris gets finer and finer as you move downstream." So while these events are infrequent, they can be quite destructive. Some residents of Southern California have had their homes damaged or destroyed by debris flows.

Many of these fans are over a mile across and they are found all over Death Valley. In fact, the vistor center at Furnace Creek is built on top of the Furnace Creek Fan. The ages of the debris found in the fans tell us that it has taken hundreds of thousands of years for these fans to build up to their present state.

The Ubehebe Crater
The Ubehebe (pronounced "You-bee-HEE-bee") is a volcanic crater located in the northern portion of Death Valley. The crater is nearly a half mile in diameter and 500 feet deep. A powerful volcanic explosion occurred about 6,000 years ago creating this massive hole in the valley floor.

The Ubehebe Crater is the largest in a series of craters found in the area. Most of the other smaller craters are less distinct than Ubehebe, with the exception of the well-formed Little Hebe crater. All of these craters were formed when molten rock came in contact with groundwater, causing a series of powerful steam explosions. The entire area has interesting volcanic and bedrock debris that was blown out of the crater.