WHERE DID IT ALL BEGIN WEAK OR STRONG Some sedimentary rocks such as shale are so soft you can crumble them in your hand Others such as quartz sandstone are so hard you can barely break them apart with a sledgehammer 왔 Shale is a rather soft sedimentary rock O ut of the three types of rock igneous sedimentary and metamorphic sedimentary is the most common It is made up of layers of small particles that are pressed and cemented tightly together CLASTIC ROCKS Different kinds of particles make different kinds of sedimentary rocks Sandstone and shale are made up of bits of other rocks and minerals and are called clastic rocks ORGANIC ROCKS Other sedimentary rocks such as coal or chalk are mostly formed by the remains of plants or animals Because they are made up mostly of things that were once alive they are called organic sedimentary rocks 왘 Coal is the largest source of energy for the generation of electricity 왘 Nearly 40 major sedimentary rock layers are exposed in the Grand Canyon 4
BRING OUT YOUR DEAD Fossils are found in sedimentary rock They are the ancient remains of plants and animals 왘 Well-preserved fossil of a prehistoric fish 왗 Limestone rock is made up mostly of calcite CHEMICAL ROCKS Minerals or chemicals form the third type of sedimentary rocks For example limestone is made up mostly of a mineral called calcite It is known as a chemical sedimentary rock spoon sand water MAKE YOUR OWN ROCK Have an adult help you with this activity You will need mixing bowl small paper cup Epsom salts Mix 1 cup of water and ½ cup of Epsom salts in a mixing bowl Stir until most of the salts have dissolved Fill a paper cup halfway with sand Now add just enough salt solution to wet the sand Let dry for two or three days Cut away the paper cup Where did the salt go How did it help form the rock 5
WEARING IT AWAY Ice wind rain flowing rivers glaciers waves and natural chemicals all wear away at human-made and natural structures on Earth The particles that fall off these structures create the sediment that can form into sedimentary rock WEATHERING Weathering is the breaking down of Earth’s soil rocks and minerals by weather chemical reactions and plants and animals The movement of rocks minerals and soil by forces such as water ice wind and gravity is called erosion HEAVY METAL The same chemicals that can eat away at rocks also break down metals One common form of corrosion is rust which you can see on cars garbage cans and other metal objects all around you 왔 Rust is a common form of corrosion 왘 Mountain river transporting large amounts of sediment 6
WHO DOO Hoodoos are sandstone structures created by weathering The capstone on top is made of harder rock than the columns It protects the softer rock underneath creating formations called rock mushrooms 왔 Hoodoos found in the badlands of Alberta Canada CORROSION Chemicals in the air whether from pollution or volcanic eruptions can make rainwater acidic This solution will eat away at many surfaces including rocks TRANSPORTATION When parts of a rock break off and wear away they are carried off by moving ice water or wind This part of erosion is called transportation The material carried away by rivers is called the load Some rivers turn brown or yellow when they are carrying large amounts of sediment DEPOSITION Glaciers carry sediment down mountains and eventually deposit them in one spot When rivers reach an ocean or a lake they slow down and also deposit the eroded sediment In deserts wind carries small sand particles long distances piling the sand into large dunes In all these cases this build-up is called deposition Where these deposits build up sedimentary rock can form 왔 Acid rain can produce cracks in limestone slabs called clints 7
