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Rocks and Geology
Geology (Ge-ol-o-gy) is the science of studying the origin, history and structure of Earth. Geologists are scientists who study rocks and ancient fossils. Rocks come in all different shapes, sizes, textures, colors and levels of hardness.
Rocks All Around
Rocks are created from one or more hardened minerals (min-er-als) that have been pressed down, or forced together from heat and pressure. What are minerals? Minerals are solid material found inside and on Earth's surface. Each mineral has a repeating pattern called a crystal (crys-tal). The most common rock-forming minerals are silicon (sil-i-con) and oxygen (ox-y-gen). These two elements are the building blocks of majestic mountains, canyons and valleys.
Different Rocks
Earth is made up of clay, sand, rocks and soil. It has three main layers--the outer crust, the inner mantle (man-tle) and its central core. On Earth's thin, rocky crust there are layers of small rocks, sand, clay and dirt particles called sediments (sed-i-ments). Over millions of years the sediment layers are compacted or pressed down to form sedimentary (sed-i-men-ta-ry) rock. Limestone (lime-stone) coal and sandstone (sand-stone) are sedimentary rocks.
Below Earth's crust lies the mantle. It consists of a thick layer of hot magma (mag-ma) or molten rock. When the hot molten rock cools, it forms igneous (ig-ne-ous) rocks. Black lava and glassy obsidian (ob-sid-i-an) are igneous rocks. Pumice (pum-ice) explodes out of volcanoes, yet it can float on water! Pumice is an igneous rock! Deep inside Earth, magma can cool down and form granite (gran-ite). With high heat and pressure, igneous or sedimentary rocks change into metamorphic (met-a-mor-phic) rocks. Limestone can "morph" or change into marble. Granite will change into gneiss.
When Minerals Are Not Rocks
Scientists describe minerals to be everything that is not a "vegetable" or "animal". Gold and silver are metal-ore minerals. Water and gas are liquid minerals. All rocks contain minerals. Yet did you know all minerals are not rocks? Quartz is a white, rock-hard mineral, yet it is not a rock. Extreme high heat and pressure can change coal into dazzling diamonds. However, diamonds are precious mineral gems, not metamorphic rocks.
Every Rock Has A Story
About 30 to 90 million years ago, oozing tree sap trapped insects, pollen, leaves, seeds and dirt. Buried under layers of hardened rock, the tree sap fossilized (fos-sil-ized) into golden-red amber (am-ber). Ancient river and seabeds thrived with marine animals and plants. Now they team with fossils buried under layers of sedimentary rock. Fossils (fos-sils) show us what animals, plants, trees and insects looked like and where they lived millions of years ago. Investigate rocks today to learn more about Earth's amazing story!
Vocabulary
Study the ROCK CYCLE diagram on the front page. Powerful forces act on certain minerals (or rocks) to form new kinds of rock. Look at the mineral on the left. Write inside the arrow a powerful force that can change the mineral. Then, in the box on the right, write in the type of rock formed by that force.
MINERAL POWERFUL CHANGING FORCE ROCK sediments magma sedimentary rock
BONUS: -- and -- rocks can melt to become magma.
Math
Rivers cut through canyons to expose layers of ancient sedimentary rocks. Tyrannosaurus Rex (Ty-ran-no-sau-rus Rex) roamed during the Jurassic Period. How old are these rocks?
1. What is the range of time for the Cretaceous Period layer? --years.
2. How many years are in both time periods? --years.
3. What percentage of years lies in the Jurassic Period?--.
4. If shale took 30 million years to develop, what is its percentage of time during the Cretaceous Period? --.
5. Why do you think there is a fossil difference between both periods?
DID...
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