Processes that Change Earth’s Surface Unit 4 Lesson 1 Processes that Change Earth’s Surface S8.D.1.1.1,2,4

Weathering Breakdown of rocks into smaller pieces called sediment 3 main causes of weathering Liquid water Ice Wind examples 2 kinds of weathering Physical Weathering Chemical Weathering

Physical Weathering rock breaks into smaller pieces but its chemical composition does not change Also called Mechanical weathering Unloading/ pressure release Weathering WIKI Other examples

Chemical Weathering The chemical composition of the rock changes Rocks break down through chemical reactions Air and water react with minerals in rock to create various chemical reactions Types of chemical weathering Feldspar to Clay Types

Erosion Process by which sediment is moved over Earth’s surface by water, wind, or ice Houses undermined by coastal erosion in Pacifica, California. Photograph courtesy of NASA.

Erosion Most erosion happens over long periods of time Erosion site Most erosion happens over long periods of time rivers carving through land takes millions of years . The Grand Canyon is an impressive example of stream erosion through rock Erosion clip

Erosion Some erosion happens very quickly after heavy rains, fast moving water can carry large amounts of sediment away heavy rains can also cause landslides Soil erosion can be prevented by planting vegetation, trees, shrubs, and other plants. Roots of these plants will help hold soil in place. Soil will not be blown away by wind or washed away by water as easily

Deposition/Sedimentation Process in which eroded sediment is dropped at another location Deposition animation Sediment may get transported thousands of miles by one of the world's major rivers, or it may just go from the top of the hill to the bottom during a landslide *Increase erosion somewhere can cause an increase of sediment elsewhere

Deposition/Sedimentation Most deposition happens when water or wind slow down

Formation of Mountains When two of earth’s plates collide, mountains can form The formation of mountains takes millions of years Video clip of mountains forming Appalachian Mountains Pocono Mountains

3 Types of Rocks Sedimentary Igneous Metamorphic

Sedimentary Rocks Form from: Sediment Remains of living things (coal) Sediment builds up and top layers put pressure on bottom layers squeezing the sediment together Over time, sediment in lower layers become cemented together to form sedimentary rock

Sedimentary Rocks Sandstone Shale Coal Limestone

Igneous Rocks Magma- molten rock underground Lava- molten rock above ground Igneous rock forms when molten rock cools and hardens If it cools slowly, large crystals form If it cools quickly, small crystals form (obsidian)

Igneous Rocks Granite Pumice

Metamorphic Rocks Form when heat and pressure change the chemical composition of a rock Rocks that are buried very deep are under extreme heat and pressures Minerals in the rock react to form new minerals Most metamorphic rocks in Pennsylvania formed from the continental collision responsible for the formation of the Appalachian Mountains

Metamorphic Rocks Slate Gneiss (nice) Forms from shale Forms from sandstone Marble Gneiss (nice) Forms from limestone Form from granite

Rock Cycle Rocks can cycle between types if exposed to: heat and pressure weathering and erosion melting and cooling

Rock Cycle Rock Cycle Animation Rock cycle Animation

Fossils Evidence that organisms existed in the distant past Can help scientists learn what ancient organisms looked like where they lived when they became extinct Can also help scientists learn about Earth’s environments in the past. Ex. Finding a marine fossil somewhere would suggest that area was once underwater Estimated that one in a million organisms become a fossil

Fossils in PA Trilobite