Tassajara Formation facts for kids
The Tassajara Formation is a special type of rock layer found in the ground. It's located in a place called the Livermore Valley in Northern California, United States. Think of it like a big, hidden part of the Earth's crust.
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What is the Tassajara Formation?
The Tassajara Formation is a geological unit. This means it's a distinct group of rocks and sediments. It's like a specific chapter in Earth's long history book.
Where Can You Find It?
You can see parts of the Tassajara Formation on the surface. These parts are in the northern, higher areas of the Livermore Valley. But most of this formation is hidden deep underground. It lies beneath the middle part of the valley floor.
How Deep Is It?
The Tassajara Formation can be found at different depths. It starts about 250 feet (80 m) (which is like 25 stories deep) below the surface. In some places, it goes down even further, up to 700 feet (200 m) deep. That's a really long way down!
What Is It Made Of?
The Tassajara Formation is made up of several kinds of materials. These include:
- Mudstone: This is like hardened mud, often brown or gray.
- Sandstone: This rock is made from grains of sand cemented together. The sandstone here is often "andesitic," meaning it contains minerals from volcanic rocks called andesite.
- Conglomerate: Imagine a rock made of many different pebbles and stones stuck together. That's a conglomerate!
- Tuff: This is a rock made from volcanic ash. Sometimes it's "bentonitic" (meaning it has a type of clay called bentonite) or "pumiceous" (meaning it contains pumice, a light, frothy volcanic rock).
The Bishop Subbasin Connection
The Tassajara Formation also plays a role in storing water. There's an underground water supply called the Bishop Subbasin. This subbasin is an aquifer, which is a body of rock that can hold and transmit groundwater. The Bishop Subbasin sits between two underground ridges. These ridges are actually parts of the Tassajara Formation. They help to create a natural container for the water.
In the northern part of the San Ramon area, the Tassajara Formation is found beneath more recent valley fill material. This means newer layers of soil and sediment have built up on top of it over time.
