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Moving Rock Weathering & Erosion

What is weathering? Video Video Weathering is a set of physical and chemical processes that change the physical and chemical properties of rocks and soil at or near the earth's surface.

More about weathering  Definition – the breakdown of rock to form sediment [very small pieces of rock] –Weathering happens to rocks that are NOT MOVING –Weathering is part of the Rock Cycle

Mechanical Weathering  BREAKS rocks into different shapes and smaller sizes  Jagged rocks usually become smooth  Mechanical Weathering Mechanical Weathering Mechanical Weathering

Abrasion  Breaking, grinding, wearing away of rock  Caused by wind and water

Ice Wedging  Freezing water in cracks expands and breaks rocks

Plate Movement  The moving and sliding of tectonic plates wear away rocks as they slide past each other

Plant Action  Wedging of roots into cracks causes cracks to become larger. As a root grows it can break apart the rock.

Chemical Weathering  Changes the chemical makeup of the rocks and minerals. Can remove certain minerals from some rocks and can change the minerals into new substances.

Chemical weathering happens when the minerals that make up a rock are changed, leading to the disintegration of the rock

 Oxidation- red brown crust is iron oxide. Forms when oxygen joins chemically with iron, can weaken and crumble rocks.

 Acid Rain Dissolving by Acids- Water that contains acids dissolves minerals.

What is erosion? Erosion is defined as the removal and movement of earth materials by natural agents. Some of these agents include glaciers, wind, water, earthquakes, volcanoes, tornadoes, hurricanes, mud flows, and avalanches.

How are erosion & weathering different? Weathering involves two processes [mechanical, chemical] that often work together to break down rocks. Both processes occur in place. No movement is involved in weathering.

In a nutshell: if a particle is loosened, chemically or mechanically, but stays In a nutshell: if a particle is loosened, chemically or mechanically, but stays put, we call it weathering. Once the particle starts moving, we call it erosion.

Water Erosion  Rainwater running of land carries away sediment leaving behind an eroded path. Over time it widens an deepens to form a stream or river.  Grand Canyon Formation Grand Canyon Formation Grand Canyon Formation

Close to Home – Canyon Lake After the Flood

Close to Home – Beach Erosion  Ocean waves and currents carry sand of one beach and deposit it later on another beach. Three feet a year in some places!

Wind Erosion  Fast-moving wind can carry sand and dust that scour and weather the surface as they strike. Wind erosion is great in dry areas. When the wind slows it drops it load, this is how sand dunes are formed.

Ice Erosion Video Video  Rivers and sheets of ice (glaciers) slowly move over land. As they travel, glaciers can move boulders the size of houses as well as small sediment. The rocks and sediments carried can carve or deepen valleys.

Gravity  Gravity causes water and glaciers to move downhill, and particles carried by water and wind settle to a stream or lake bed to the ground. Gravity can also directly causes erosion in the form of landslides and mudflows

Deposition  Eroded rock particles are dumped off in a new location  How does it deposit? –When it slows down, dumps off rocks to form dunes/piles  How does it deposit? –Where water slows down, rocks are dumped off –Form deltas/fans or plains

Deposition –Rocks dump when glacier melts –Makes moraines and drumlins –Carried particles are dumped on shore –Form beaches, sand bars, spits

Sandbars

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