Little Walker Caldera facts for kids
A caldera is a very large, bowl-shaped hole in the ground. It forms when a volcano erupts and then collapses. The Little Walker Caldera is one of these huge depressions. It is found in the eastern part of the Sierra Nevada mountains. It is also very close to the Sweetwater Mountains.
What is the Little Walker Caldera?
The Little Walker Caldera is truly enormous! It measures about 18 kilometers (or 11 miles) across. That's a really big hole in the Earth! It got its name from the nearby Little Walker River. If you travel on U.S. Route 395 in California, you will cross the northern edge of the caldera. This is just west of a place called Devil's Gate Pass. Another road, California State Route 108, also follows more of the caldera's northern boundary.
When Did It Last Erupt?
The Little Walker Caldera had its last major eruption a very long time ago. This happened about 9 million years ago. During these eruptions, a type of lava called andesitic lava flowed out. Also, a material called tuff was released. Tuff is like rock made from volcanic ash.
These volcanic materials were very thick. They spread far and wide. You can find them hundreds of feet thick in places like Antelope Valley. This valley is about 20 miles north. They also reached Bridgeport Valley to the south. And they even went as far as Sonora, which is 60 miles to the west!
The lava flows near Sonora are easy to see from California State Route 108. These ancient lava flows followed old streambeds. These streambeds used to have a lot of gold. Today, people have found rich gold deposits by digging under these old lava flows.
Is It Still Active?
The Little Walker Caldera is considered an extinct volcano. This means scientists do not expect it to erupt again. However, it is not completely quiet. It still has a lot of hot spring activity. Hot springs are places where hot water comes up from underground. The caldera also experiences occasional earthquakes.
Some parts of the Little Walker Caldera actually overlap with the northern edge of Yosemite National Park.
