Weathering, Erosion, & Deposition

The Cycle of Changing Earth’s Surface Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface Weathering-wears down the Earth’s surface Erosion-moves the Earth’s surface (acts as a bridge between the weathering and deposition) Deposition-builds up the earth’s surface

Please draw this in your notes Weathering Erosion Deposition

Weathering The breaking down and/or wearing away of earth materials (rocks) into smaller pieces Must occur before erosion can happen No movement is involved Sediments- naturally-occurring material that is broken down by processes of weathering; small/tiny pieces of rock

Physical Weathering Physical/Mechanical weathering-the breaking down of rocks into smaller pieces (wind, flowing water, ice, gravity, animals/plants, temperature changes) Physical Weathering The steep walls here were carved out by moving water Palo Duro Canyon in the High Plains EcoRegion

Physical Weathering Enchanted Rock in the Llano Uplift Ecoregion Exfoliation-warming and cooling of rocks over time causes rocks to peel into sheets

Chemical Weathering Chemical weathering-occurs when chemical reactions dissolve the minerals in rocks or changes them into different minerals (rusting, acid breakdown, etc) Chemical Weathering This cave was formed by slightly acidic water dissolving the limestone

Chemical Weathering Natural Bridge Caverns in Texas

Lets compare Please draw a Venn diagram and compare chemical and physical weathering. How are they similar/different?

Erosion The movement of weathered earth materials by moving water, wind, gravity or ice Ex: waves causing beach erosion (shoreline of Texas is disappearing) running water http://www.glo.texas.gov/what-we-do/caring-for-the-coast/coastal-erosion/causes-of-erosion.html Ex: sand storm wind Ex: rain causing a mudslide running water and gravity Ex: landslide gravity Ex: rain carrying soil and gravel down a driveway running water and gravity

Erosion Galveston Texas before/after Hurricane Ike

Erosion A gorge is a ravine with nearly vertical walls. This gorge was cut when heavy rains pushed a flood over Canyon Lake Dam in central Texas in 2002.

Erosion The Bernard Glacier in Alaska's Saint Elias Mountains looks like a huge alpine highway. Glaciers are slow but highly effective shapers of the land, essentially carrying away anything in their path—from soil and rocks to hills and even the sides of mountains

Why care about erosion? Human activities such as construction increase the rate of erosion 200, even 2,000 times that amount. When we remove vegetation or other objects that hold soil in place, we expose it to the action of wind/water and increase its chances of eroding The loss of soil from a construction site results in loss of topsoil, minerals and nutrients, and it causes ugly cuts and gullies in the landscape. Surface runoff and the materials it carries with it clog our culverts, flood channels and streams. Sometimes it destroys wildlife and damages recreational areas such as lakes and reservoirs.

Bare Slopes vs. Vegetation Stabilized Slopes Mudslide danger Loss of topsoil Clogged storm drains Flooding problems Expensive clean up Eroded or buried house foundations Soil in place Less clean up Minimum erosion Protection for house foundations

Landslides Landslides- a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments.

Deposition The process of eroded earth materials (sediments) being deposited in a new location Ex: delta-where sediment is deposited where a river flows into an ocean or lake builds up a landform Ex: sand dune-a deposit of wind blown sand

Deposition Desert winds sculpted these gentle swirls out of the limestone hills in Black Gap Wildlife Management Area, Texas. This remote, 100,000-acre (40,470-hectare) area in West Texas contains some of the lowest, driest, and hottest areas in the Chihuahuan Desert

Deposition Deposition area from the Rio Grande River The Red River carries sediments, and drops some along the way