Page 8--Metamorphic Rocks


Rocks that have been changed from one kind of rock to another by heat and pressure are called metamorphic, which is Latin for "changed form." Limestone changes to marble; shale to slate, schist, and gneiss; and sandstone to quartzite. Marble, slate, and quartzite are much harder rocks than limestone, shale, and sandstone. Metamorphic rocks are rare in Kansas. Quartzite, which is found in a small area in Woodson County, is the only native metamorphic rock found at the surface.

Quartzite boulders can be found throughout northeastern Kansas, but they were not formed there. Glaciers carried the rocks in from South Dakota, Iowa, and Minnesota. They are red, brownish red, or purple.

Igneous Rocks

Igneous rocks are formed when a hot liquid, called magma, cools and changes from a liquid state to a solid state. They may form slowly underground or rapidly at the Earth's surface. When magma reaches the surface, it is called lava. Lava flows out of a volcano and quickly hardens after an eruption. Although most lava reaches the surface through volcanoes, it may also flow out of deep cracks in the earth without building a mountain.

Kansas doesn't have an active volcano, but lava did flow onto the surface as recently as 90 million years ago when dinosaurs still roamed the Earth. Hot magma forced its way up from over 100 miles below the Earth's surface in two small areas of eastern Kansas. The hot liquid, which spread upward through cracks in other underground rocks, cooled and hardened, forming a rock called lamproite in Woodson and Wilson counties and one called kimberlite in Riley County.

In one area of Riley County, lava flowed onto the surface but a volcanic cone was never formed. The kimberlite formed from the lava is now buried. Lamproite and kimberlite found at the surface in Kansas were exposed when the rock above was eroded away. Diamonds have been found in kimberlites and lamproites in other parts of the world, but none has been found yet in Kansas.

Granite, another type of igneous rock, has been found mixed with lamproite in Woodson County. It is older than the surrounding surface rocks and was formed deep in the Earth. Lamproite magma carried it toward the surface, where it is now exposed.

Some igneous and metamorphic rocks have traveled into Kansas from other places. Volcanic ash, basalt, granite, and quartzite have been carried in by wind, glaciers, and water.

Meteorites

One type of rock found in Kansas was not formed anywhere on Earth. Meteorites have the most unusual origin of any sediment carried--or, in this case, dropped--into Kansas. Meteors are rocks in outer space that usually vaporize before reaching the Earth's surface. As they enter the atmosphere and begin to disintegrate, meteors are seen as streaks of light called shooting or falling stars. The few meteors that do reach the Earth's surface are called meteorites.

Identifying meteorites in Kansas is easier than in other places, because they don't look like other Kansas rocks. Meteorites usually have a burned appearance, are pitted, and are denser than other rocks. Iron meteorites, consisting of heavy metals, iron, and nickel, are the easiest to identify. Stony meteorites are harder to identify because they look like volcanic rocks. Because Kansas has few volcanic rocks and lots of wide-open spaces, many meteorites have been found in the state.


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Kansas Geological Survey
Placed online Feb. 1, 1996
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