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Name:_____________________________________ Class:___Earth Science_______ Period/Block:________________________________ Date:______________________________________ Class Notes: S6E5 g. Describe how fossils show evidence of the changing surface and climate of the Earth h: Describe soil as consisting of weathered rocks and decomposed organic material. What is a fossil? What do fossils tell us? What are the conditions needed for fossil formation? How are fossils found? What are the main types of fossils? • A fossil is the preserved remains of a onceliving organism. • Fossils tells us a great deal about plants and animals in the past. • They also provide evidence about how Earth’s surface has changed over time. • Fossils help scientists understand what past environments may have been like. • Tells us about the age of rocks. • Quickly covered or buried by sediments • Has to be protected from scavengers or forces that cause destruction • Most fossils found are the hard part of once living organisms because it takes longer to decompose. • The activity of humans. Ex. Digging Earth’s processes exposes them on the surface. • Weathering • Erosion • Tectonic forces causes them to be uplifted • Petrified/permineralized remains: Forms when minerals from water seep into holes/cracks of bone. When water evaporates, only hardened minerals are left. • Casts and molds: A mold (impression) forms when hard parts of an organism are buried in soft sediment, such as mud, sand, silt, or clay. A cast forms when hard part (shell) is dissolved and a copy is made from hardened minerals that fill the once empty space. • Carbon Films: An animal dies and get buried, heat and pressure squeezes out gases and liquid from the body. What is left is the element carbon. It looks like silhouette of the original organism. • Trace fossils: Forms when an animal steps in soft sediment (mud or silt) making a footprint and becomes buried in layers. The sediment eventually becomes rock. Paleontologists use these clues to determine size, weight, and how they lived. • Original remains: Occurs when most or all of an animal/plant is trapped in tar, amber or ice. This preserves the animal or plant from decaying. What is the law of superposition? What is soil? How is it made? How are soils classified? What is soil composed of? Soil Profile • Using relative dating, determining age of rocks based on the location of fossils, the law of superposition says that rocks are deposited layer upon layer. Oldest are laid first. • Soil is a _________ of weathered rock, decayed organic matter, mineral fragments, _______, and air. 1. ________ breaks down rocks or minerals on our surface, it creates a layer of rock sediments. 2. Over time, the sediments break down even more creating very fine (small) particles. 3. _______ and _________ add organic matter, wastes and dead plant material, to the rock fragments. • • Soils are classified by their size List particle by size from largest to smallest Soil is made of rock and mineral fragments, organic matter, air and water. Ex. lawn clippings, leaves, stems, branches, moss, algae, any animal parts, manure, sawdust, insects, earthworms and microbes The decayed organic matter turns into a dark-colored material called humus. Humus serves as a source of nutrients for plants. The layers of different soil are called _______. On the top of A Horizon are leaves, twigs and other organic matter called ________. Horizon A is also called ____________. __ Horizon has the darkest soil because of the decayed organic matter. B Horizon has soil that is lighter in color because less _______ matter.(less fertile) B Horizon gets minerals from A horizon by the process of _________. C Horizon is the lightest and _______ soil layer. The C Horizon contains partially weathered _____ and very little organic matter. 5 factors that affect soil formation What is found beneath the horizons? __________: a layer of solid rock that contributes/adds to soil; also called ______ rock. 1. _____________: Soils in deserts contain little organic material and also are thinner than soils in wetter climates. Areas that are wetter produce more plants needed to add organic matter for healthier soil. 2. Slope: Steep hills have poor soil as gravity pulls soil that forms downhill. 3. _______________: Type of vegetation affects soil formation. As it decays, it may add different nutrients back into the soil. Little vegetation=less fertile soil. 4. Types of rock: Rock type affects the type of vegetation that grows in a region. As different rocks provide different types/amounts of nutrients the soil may vary. 5. Time: The longer a soil has been forming, the thicker it becomes.