CHAPTER 4 NOTES -WEATHERING AND EROSION- LESSON 4.1: TYPES OF WEATHERING

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CHAPTER 4 NOTES -WEATHERING AND EROSION- LESSON 4.1: TYPES OF WEATHERING WEATHERING Weathering- the process by which rocks are broken down by the forces of nature.

1 CHAPTER 4 NOTES -WEATHERING AND EROSION- LESSON 4.1: TYPES OF WEATHERING WEATHERING Weathering- the process by which rocks are broken down by the forces of nature. - the breakdown of large rocks into fragments by physical forces. o Physical weathering does not change the of the minerals that compose a rock. - when minerals in rock react chemically with air or water, the minerals weaken or even dissolve away, causing the rock to crumble. PHYSICAL WEATHERING - occurs when rainwater or melted ice soaks into tiny cracks in a rock and freezes. The sudden expansion of ice as it freezes can split rock. play a part in physical weathering as roots can split rocks as they grow into their tiny cracks. or carrying sand or grit can weather rocks by repeatedly striking them with hard mineral fragments. 1

2 - the process of breaking or peeling away of rock in layers. Exfoliation produces smooth, rounded domes of rock. The broken off fragments are referred to as talus. CHEMICAL WEATHERING The main agent of chemical weathering is. o In nature, water has a ph of about 5.6, making it. Weak acids, like carbonic acids, and stronger acids, such as sulfuric acid, can cause chemical weathering. o The stronger the acid, the the weathering. - the process where oxygen in the air and water reacts with minerals like calcium, magnesium, and iron to form new compounds. o When rocks with iron are weathered by oxygen, the rock appears to at the surface, giving it a reddish-brown color and weakening the rock s surface. Chemical weathering changes the of the original minerals. Chemical weathering is generally a process. Porous rocks generally weather more than nonporous rocks. Fine-grained rocks weather than coarse-grained rocks. Weathering occurs in hot, moist climates and slower in dry, cold areas. LESSON 4.2A: WATER EROSION WATER EROSION - carrying away of rock fragments by wind or running water. o - formed as a result of erosion beneath the earth s surface. - the process where eroded rock fragments are deposited in a new location. 2

WATER EROSION (continued) The process of erosion often begins with. - excess water that pools on the ground and runs downhill, following a heavy rain.

Melting snow and ice, paired with heavy rains, gathers in low spots to form - narrow, shallow cuts in the soil.

3 WATER EROSION (continued) The process of erosion often begins with. - excess water that pools on the ground and runs downhill, following a heavy rain. Runoff strips away a thin sheet of topsoil from the surface of the land in a process called sheet. may also be a major source of runoff. Melting snow and ice, paired with heavy rains, gathers in low spots to form - narrow, shallow cuts in the soil. Additional water can cause rills to deepen and carve out channels in the ground- a process called. Continued gullying will form a, which fills with wildly flowing water during a rain storm, but dries up during fair weather. - large streams that carry water from mountains to the sea. Most rivers begin with dozens of small brooks or streams in the highland regions. These brooks and streams form the, which is the source of a river. - the material carried by a stream. The load that a stream can carry depends on its. - a relatively large stream and any smaller streams that flow into it. - the region of land drained by a drainage system. (aka: ) - raised land area that separates two adjoining drainage basins. 3

4 LESSON 4.2B: A RIVER S COURSE - streams that feed into a river at various points along its course, increasing the amount of water it carries. - the level of the land that borders a river and is covered by river water in flood time. - natural ridges formed when flood waters drop sediments along the edges of the river s channel. - winding, looping curves formed by rivers on a floodplain. o Meanders are constantly changing form and position as the river sediment on the of each curve and sediment on the. - formed when a meander is becomes cut off from the rest of the river. - a fan-shaped or triangular deposit extending from the mouth of the river into the sea. o Formed as a river deposits large loads of sediments. - similar to a delta, but formed in a desert by shortlived streams that result from occasional desert thunderstorms, leaving large loads of rock and sediment at the bottom of mountains. 4

LESSON 4.2C: EROSION BY GROUNDWATER AND SEA EROSION BY GROUNDWATER - large caves formed by underground erosion. o - a large, icicle-like mass of calcium carbonate.

5 LESSON 4.2C: EROSION BY GROUNDWATER AND SEA EROSION BY GROUNDWATER - large caves formed by underground erosion. o - a large, icicle-like mass of calcium carbonate. o - mineral water dripping from the ceiling to form a cone-shaped structure on the cave floor. o - when a stalactite and stalagmite grow together until they join. - a large funnel-shaped depression in the ground. Formed when the roof of a cavern collapses. - regions of the earth s surface where limestone is exposed and abundant. o Caverns are frequently associated with. o and sink holes are common geologic features in karst regions EROSION BY SEA - form or grow as waves, currents, rivers or streams deposit sand and other sediments. o Natural disasters can reshape the coastline very quickly. - offshore ridges of sand (or gravel) built up by waves and currents. - narrow, sandy islands off the coast of the mainland, formed by erosion. o The water between the barrier island and the coast is called a. - high ridges of rock and land that project out into the sea along deep-water shorelines. - vertical face of rock left behind after erosion. 5

6 - formed as waves erode deep indentations in the surface of softer rock. - natural formations of rock that arch out into the water from the coast. Formed by the continual erosion of sea caves. - forms when a sea arch collapses. LESSON 4.3A: ICE, WIND AND WASTING EROSION BY GLACIERS - a thick sheet of ice that slowly moves under its own weight. o On level ground, glaciers gradually flatten and spread outward under their own weight. Types of Glaciers o - vast sheets of ice that cover immense areas of relatively flat land. There are 2 major continental glaciers on Earth: one covers the continent of, and the other covers most of. - smaller sheets of ice. o - aka: - rivers of ice that flow slowly down from mountainous regions into valleys. Much more numerous. Valley glaciers scoop out a huge bowl shaped depression, called a, as it slides down the landscape. o A sharp ridge divides two cirques, known as an. o When three or more cirques cut into a mountain peak, they transform it into a sharp, steeple-shaped point called a. - formed when seawater fills a valley carved out by a glacier. 6

7 EROSION BY GLACIERS (continued) - deep grooves and scratches in the bedrock produced as large, hard rocks are pushed along by a glacier - huge chunks of broken rock left behind after a glacier retreats (or melts). - an accumulation of till left by a glacier. - low hills formed as new glaciers overrun moraines from a previous season. - deposits formed as streams of water melt beneath a glacier, washing sand and other sediments from beneath the ice. - large holes left from the melting of huge chunks of glacial ice lodged in till or outwash. o When a kettle fills with water, it forms a - period of widespread glaciation. LESSON 4.3B: EROSION BY WIND EROSION BY WIND - produces features such as sandstone arches and uniquely shaped rocks. o - the process where wind transport sediments over long distances. o - the process where particles are lifted for short distances and dropped abruptly. o - the process where particles that are too heavy to be lifted, are rolled in short bursts. - the removal of loose particles of sand and soil by the wind, leaving only the largest pebbles behind. 7

8 o Over time, the level of land s surface will decrease until only a layer of pebbles and larger rocks, too heavy to be lifted, remain. The resulting surface is called. - shallow depressions formed when wind blows materials away. - carry coarse sand particles and fine particles of dust. o Usually occur in. - only carry dust. o Usually occur in areas experiencing. o Areas where the soil is blown away are, but areas where soil is deposited are. - huge load of clay and silt deposited when a dust storm weakens. - huge heaps of sand removed by deflation and deposited in a new location. o Dunes form when sand collects around an obstacle that slows the wind (ex: rocks or vegetation) o Sand Dunes can come in several shapes: - most common, sickle-shaped dunes. The point of the dune faces away from the wind. - arc shaped dunes with an open end that points toward the wind. - resemble ocean waves. Form when enough sand is available for crescentic dunes to merge together. - occurs in areas with abundant sand and wind coming from several directions. o - the eroding action of windblown sand. 8

9 LESSON 4.3C: EROSION BY GRAVITY MASS WASTING - the process in which gravity causes the downslope movements of rock soil, volcanic ash, snow, or ice. o - very slow movement of soil and rock fragments. Caused by soil expansion and contraction as a result of changes in temperature and moisture, or by action of plants and animals. - rapid movements of loose, water-saturated soil. The most fluid and fastest type of mass wasting. o Form when heavy rainstorms flood dry desert channels creating fluid mud that destroys everything in its path. - a mass of ice and snow that abruptly dislodges from a mountain face. o Triggered by sharp noises or other disturbances. - sudden slides of huge masses of rock or soil down a slope. o Landslides are classified according to the type of material that falls. - rock fragments and other loose materials found in coarse soil. - fine soil and small pebbles. - consists primarily of bedrock. - when individual rock fragments abruptly break off the sides of a steep cliff after weathering. PREVENTING EROSION in exposed soil Protect plowed fields with. - modifying smooth slopes into a stair-step slope. Creating using trees, tall plants, or fences. 9

10 - planting alternating strips of erosion-prone and erosion-preventing crops. Building artificial and flood-controlled dams. Planting dune-living. Building windbreak fences or - objects designed to reduce the force of waves. 10

1/6/ th Grade Earth s Surface. Chapter 3: Erosion and Deposition. Lesson 1 (Mass Movement)

1/6/ th Grade Earth s Surface. Chapter 3: Erosion and Deposition. Lesson 1 (Mass Movement) Lesson 1 (Mass Movement) 7 th Grade Earth s Surface Chapter 3: Erosion and Deposition Weathering the chemical and physical processes that break down rock at Earth s surface Mechanical weathering when rock