What is the MAJOR agent of erosion that has shaped Earth’s land surface? Moving water Water moving over land’s surface is called runoff. This may cause sheet erosion.
The amount of rain an area receives. • Vegetation - grasses, shrubs & trees reduce runoff • Type of soil - some absorb more water than others • Shape of the land – steep slopes have more run-off, which causes more erosion • How people use the land – parking lots & crop removal increase run-off The amount of water runoff depends on 5 main factors:
Rills & Gullies Rills are tiny grooves in the soil that grow larger forming gullies. A gully is a large groove or channel in the soil that carries runoff after a storm. It moves soil & rocks. Gullies only contain water after it rains.
Streams & Rivers Gullies join together to form a larger channel called a stream. Water continuously flows here and rarely dries up. Small streams may be called creeks or brooks. Small streams flow together to form a large stream called a river.
Rill, Gully, Stream Rill erosion at a construction site. Gully erosion in a pasture. Stream
Rivers cause erosion and create valleys, waterfalls, flood plains, meanders and oxbow lakes. Deposition along a river forms alluvial fans and deltas.
Not all rain water evaporates or becomes runoff. How does water get underground? Water soaks into the ground, filling openings in the soil and trickling into cracks & spaces in layers of rock. Groundwater causes which type of erosion? Chemical weathering What acid forms when carbon dioxide & water combine? Carbonic Acid This weak acid can break down limestone that will gradually hollow out pockets in the rock. Over time, the pockets develop into large holes called caves or caverns.
What are stalactites? Calcite deposits that hang from the cave’s roof likeicicles What are stalagmites? Cone-shaped calcite deposits that build up from the cave floor
KarstTopography A type of landscape that is created in a region where a layer of limestone near the surface forms deep valleys, caverns and sinkhole
A glacier is any large mass of ice that moves slowly over land • Forms in areas where more snow falls than melts. • Move slowly on land and Shape the land • Glaciers move due to the force of gravity. • 2 types: • Continental Glaciers • Valley Glaciers • Ice Ages – when large parts of Earth were covered with Continental glaciers
Plucking - The process by which a glacier picks up rocks as it flows across the land. Abrasion - As a glacier drags the rock along, the land is gouged & scratched Till - Deposits of sediments left behind as a glacier melts (clay, silt, sand, gravel, boulders)
Moraine Ridge that forms by the till deposited at the edge of a glacier Example: Long Island in NY is a terminal moraine
Kettles Small depressions left in areas when chunks of ice are left in glacial till • They fill in with water and form ponds or lakes • Common in Minnesota
Erosion by Waves Waves shape the coast through erosion by breaking down rock and transporting sand and other sediment. They erode hard, rocky areas of the coast that jut out just like jagged mountains that are eroded over time.
Deposits by Waves How do waves deposit sediment? as they slow down Beaches, spits & barrier beaches are formed from these deposits.
What is a Spit? A beach that projects out into the water like a finger. How do spits form? As a result of longshore drift depositing sediments along a coast Sandbars or Barrier Beaches: What are they? Long ridges of sand Where are they found? They run parallel to the beach.
Landforms Created by Wave Erosion Sea Cave- Formed as wave action hollows out a cliff.
Landforms Created by Wave Erosion Sea Arch- They form when a sea cave on either side of a headland join.
Landforms Created by Wave Erosion Sea Stack- They are left standing when a sea arch collapses.
Wind Erosion • Faster the air flows, more erosion • Erodes more rapidly if wind blows constantly from one direction • 2 TYPES OF WIND EROSION • ABRASION and DEFLATION (Removal of fine particles by wind )
SAND DUNES are ridges of wind deposited sand The formation of sand dunes depends on: - amount of sand - speed & direction of wind - occurrence of vegetation LOESS -Finely textured sediment wind-blown long distances