Confidence Hills facts for kids
Quick facts for kids Confidence Hills |
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 Location in California
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| Highest point | |
| Elevation | 137 m (449 ft) |
| Geography | |
| Country | United States |
| State | California |
| District | Inyo County |
| Range coordinates | 35°51′22.857″N 116°38′23.132″W / 35.85634917°N 116.63975889°W |
| Topo map | USGS Confidence Hills West |
The Confidence Hills are a small mountain range. You can find them in the Mojave Desert in southern Inyo County, California.
They got their name because of how they were formed. They show special shapes called "flower structures." These shapes developed in ancient lake and river sediments. For millions of years, the Death Valley area has been sinking. This made it a natural collection spot for water flowing from nearby mountains and deserts. During the Ice Ages, water from the Sierra Nevada mountains flowed into a series of lakes. These lakes included Lake Owens, Lake China, Lake Searles, Lake Panamint, and finally Lake Manly. Water from the Mojave River also drained into Death Valley. This process started less than one million years ago.
The rocks in the Confidence Hills are between two parts of the southern Death Valley fault zone. These rocks tell a story of Earth's history. Scientists can date them using volcanic ash layers and magnetic records. This record covers a time from about 2.2 million years ago to less than 1.5 million years ago. The rocks include fine-grained gypsum and clay. They also have sandstones and conglomerates. These were laid down in ancient lakes, dry lakebeds, and river fans. Volcanic ash layers are also found there. The rocks form a series of folds. These folds are part of a larger structure called an anticlinorium.
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How Confidence Hills Formed
The Confidence Hills were mostly formed by layers of sediment building up. These layers include silts, fine sands, and clay. They also have a lot of gypsum. These materials came from ancient lakes, dry lakebeds, and rivers. Scientists use these different layers to understand the formation of the hills.
Lower Layers
The lower part of the Confidence Hills has thick beds of gypsum. These beds are very strong. They form the tops of ridges. They also act as important markers for geologists. This lower section is visible because of an upward fold in the rock layers.
Middle Layers
The middle part of the Confidence Hills has fine sands and banded gypsum. In the northern part of the hills, this section has more silt and clay. It still contains banded gypsum. Scientists found signs like salt crystal shapes and cracks from drying. This shows that these middle layers were sometimes exposed to the air. The boundary between the lower and middle layers is gradual. It is marked by the highest thick gypsum bed. This middle section also contains volcanic ash layers. One important ash layer is called the Huckleberry Ridge ash. It is about 41 centimeters thick. Its grey color helps scientists identify it in the southern canyons.
Upper Layers
The upper part of the Confidence Hills is different. It does not have banded gypsum. Instead, it has red-brown silt and sand. There is one thick gypsum bed that stands alone. This bed is a useful marker in the younger rocks. The boundary between the upper and middle layers is where the highest banded gypsum is found. The sand near this boundary is green and red. These soils are well-sorted, meaning the grains are all about the same size. In the northern part, these upper layers are thicker. They also include ancient soils and ash layers.
Volcanic Rocks
Some parts of the middle layers contain volcanic rock pieces. These are mostly basalt. These volcanic rocks are found in the northwestern part of the area. They become thinner towards the south. The rock pieces are held together by a dark, sandy material. This suggests they came from the same volcanic source. These volcanic layers were likely deposited by a fan of sediment. This fan gradually turned into stream-reworked sediments. Scientists believe that the northern part of the Confidence Hills might have been the source of these volcanic rocks.
Folding and Faults
A large, uneven fold runs through the Confidence Hills. Its center line is almost parallel to a fault line in the southern region. The rock layers near the top of this fold are overturned. They also show tight, zigzag folds. This suggests that the folding happened when there wasn't much weight on top of the rocks. There have been reports of salt in the center of this large fold. After heavy rains, salt can appear on the surface. Also, sinkhole-like shapes have been seen. The fold in the Confidence Hills has two smaller folds that come together in the middle. This gives the rock layers an hourglass shape. The folds in the southern part dip towards the north and northwest. Scientists believe the Confidence Hills formed due to sideways movement along a fault. This movement caused the rocks to stretch and fold.
