Shale facts for kids
Shale is a common type of rock that forms from mud. It's a sedimentary rock, which means it's made from tiny bits of other materials that settle and harden over a long time. Imagine mud at the bottom of a lake or ocean; over millions of years, it gets squished and cemented into shale.
This mud is a mix of tiny pieces. It contains flakes of clay minerals and small fragments of other minerals. These include quartz and calcite. Shale is special because it often breaks easily into thin, flat layers. This feature is called "fissility," meaning it likes to split.
Shale and similar rocks called mudrocks hold most of the organic matter found in all sedimentary rocks. This organic matter is made from ancient plants and animals. Some shales, known as black shales, are very dark. They form in places where there is no oxygen, like deep, still water. These black shales contain lots of carbon and minerals like pyrite, which gives them their dark color.
How Shale Forms
Shale usually forms in very calm water. You can often find it in places like lakes, lagoons, and river deltas. It also forms on floodplains and in quiet waters offshore from beaches. Sometimes, it can even form on the continental shelf in deep, still parts of the ocean. This process of mud turning into hard rock can take millions of years.
Black Shales and Metals
Black shales are dark because they have a lot of carbon that hasn't been exposed to oxygen. They form in environments with very little or no oxygen. These conditions are found in stagnant (still) water. Black shales are common in some ancient rock layers from the Paleozoic and Mesozoic eras.
Some black shales can also contain many heavy metals. These include molybdenum, uranium, vanadium, and zinc. These metals might have slowly built up in the mud over a very long time.
Images for kids
-
Sample of drill cuttings of shale while drilling an oil well in Louisiana, United States. Sand grain = 2 mm in diameter
-
Color chart for shale based on oxidation state and organic carbon content
-
Shale in Potokgraben, the Karawanks, Austria
-
Splitting shale (Messel oil shale) with a large knife to reveal fossils
-
Weathering shale at a road cut in southeastern Kentucky
See also
In Spanish: Shale para niños
