Weathering, Erosion, & Deposition

1. Weathering, Erosion, & Deposition Learning Target: I can analyze the effects of weathering, erosion, and deposition on the environment in Texas Ecoregions.

2. 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

3. Please draw this in your notes

4. 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

5. 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

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

7. 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

8. Chemical Weathering Karst Topography—an area where there is a layer of limestone near the surface that groundwater erosion can significantly change the shape of the land. Deep valleys and caverns are common, but surface streams are rare because the water sinks easily down into the weathered limestone. Sinkholes are common.

9. Lets compare • Please draw a Venn diagram and compare chemical and physical weathering. • How are they alike? How are they different? Physical weathering Chemical weathering

10. 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

11. Erosion Galveston Texas before/after Hurricane Ike

12. 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.

13. 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

14. 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.

15. 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

16. 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.

17. 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

18. 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

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

20. What is an ecoregion? A relatively large unit of land or water that is characterized by a distinctive climate, ecological features and plant and animal communities (Source: National Geographic’s Strange Days on Planet Earth

21. For Review Weathering & Erosion