CHAPTER ONE What Is Erosion If you visit any national park in the U S you could see great canyons towering pinnacles or a cave deep below the Earth’s surface Many of these formations came from soil deposited in layers and cut through by water Others formed as water wind and ice moved over or through rock endlessly changing it Moving water created the cliffs of Bryce Canyon and wore away the rock of Niagara Falls Mammoth Cave grew as rainwater combined with carbon dioxide slowly dissolved the rock Mammoth Cave in Kentucky is a huge cave system with over 400 miles 644 kilometers explored 4
Niagara Falls has eroded so much rock that the falls are now seven miles 11 2 kilometers from their original location After a flood rapid changes become visible in the surrounding land Soil and pebbles wash away and tumble along the river bottom Mud deposits cover the topsoil Erosion moves the materials that form the earth from one place to another This process creates changes that shape the earth 5
Rain and snow push loose rock and soil or sediment down a mountain or along a stream Soil washes away Gravity pulls tons of rocks and soil down a slope in a kind of erosion called mass wasting When moving water or wind speed slows the sediments drop Soil deposits can build up land like deltas and wetlands Large rock piles from rockfalls create cone-shaped talus at mountain bases 6
Heat from the core melts the rock in the middle layer the mantle This heat sets up currents that move the molten rock The motion slowly moves the plates on top of the crust The plate motions create disturbances in the crust Crust Upper Mantle Lower Mantle Outer Core Inner Core 7
