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Erosion of Earth’s SurfaceAgents of ErosionImagine looking over the rim of the Grand Canyon at thewinding Colorado River below or watching the sunset overUtah’s famous arches. Features such as these are spectacularexamples of Earth’s natural beauty, but how can canyons andarches form in solid rock? These features and many other naturallandforms are a result of erosion of Earth’s surface. Erosion is thewearing away and removal of rock or sediment. Erosion occursbecause gravity, ice, wind, and water sculpt Earth’s surface.GravityGravity is a force that pulls every object toward every otherobject. Gravity pulls everything on Earth toward its center. As aresult, water flows downhill and rocks tumble down slopes.When gravity alone causes rock or sediment to move down aslope, the erosion is called mass movement. Mass movementscan occur anywhere there are hills or mountains. One placewhere they often occur is near volcanoes, as shown in Figure 8.Creep, slump, rock slides, and mudflows are four types of massmovements, as seen in Figure 9.■ Identify agents of erosion.■ Describe the effects of erosion.Erosion shapes Earth’s surface.Review Vocabularydeposition: dropping of sedimentsoccurs when an agent of erosioncan no longer carry its loadNew Vocabulary• erosionmassmovement• creepslumpdeflation• abrasionrunoffFigure 8 The town of Weed,California, was built on top of alandslide that moved down thevolcano known as Mount Shasta.LandslideYreka597MountShastaWeed0 15 km323USGS