Focus: Weathering and Erosion/Begin Soil Earth History: Day 22 Focus: Weathering and Erosion/Begin Soil 12/13/18 Science starter: Copy and answer. A rock formation in a land area contains fossils. Over time, tremendous heat and pressure change the formation to produce a harder rock formation without fossils. Which change in rock type has occurred in this land area? *Igneous rock has turned into sedimentary rock *Igneous rock has turned into metamorphic rock *Sedimentary rock has turned into igneous rock *Sedimentary rock has turned into metamorphic rock.

Plan for the Day Review key concepts related to weathering and erosion. Review homework Review quiz

Homework None!

What are the causes and effects of weathering and erosion? E.Q. What are the causes and effects of weathering and erosion?

Let’s go over key concepts about “Weathering and Erosion” Let’s go over key concepts about “Weathering and Erosion”. Take out your packet. Let’s review it.

Weathering and Erosion – Key Ideas Weathering is the wearing away or breaking of rock, soil, and minerals into smaller pieces. Weathering can occur due to chemical and mechanical processes. Example of weathering: Wind, water, ice, and gravity cause small pieces of rock to break off the side of a mountain. Erosion is the movement of particles away from their source. Example of erosion: Wind carries small particles of rock away from the side of a mountain.

Weathering – Chemical and Mechanical Processes *Mechanical Weathering – decomposition of rock and soil due to mechanical forces – pushes and pulls, impacts -Ex: wind, water, ice/frost, gravity, compression and contraction of materials due to heat *Chemical Weathering – decomposition of rock and soil due to chemical reactions -Ex: acid rain wears away statues and buildings; oxidation causes metals to rust

Factors Affecting Weathering Climate Temperature Moisture/ice Wind Topography -Mountainous, flat, coastal Type of rock Living organisms (which really could go under climate too)

Mechanical Weathering

Glaciers and mechanical weathering/erosion Glaciers are enormous masses of ice and snow. Glaciers transport material as they move (erosion), carrying broken rocks and soil debris far from their original places. They also sculpt and carve away the land beneath them (weathering). A glacier's weight, combined with its gradual movement, can drastically reshape the landscape over hundreds or even thousands of years. https://nsidc.org/cryosphere/glaciers/questions/formed.html

Ice and gravity are powerful erosive forces.

Gravity can cause abrasion weathering as falling pieces of rock break other rock.

How do living organisms cause mechanical weathering How do living organisms cause mechanical weathering? Discuss with your partner and be prepared to share.

How Organisms Contribute to Mechanical Weathering Tree and plant roots and lichen (fungus/algae) filaments grow in cracks of rocks, creating pressure that weakens the rock, causing it to weather. (Root pry)

Thermal Expansion

Temperature and Weathering

Mechanical Weathering by Water Frost wedging

Mechanical Weathering by Wind https://www.google.com/search?rlz=1C1GCEV_en&biw=1366&bih=622&tbm=isch&sa=1&ei=5ZIOXO3_FI20tQWutqgQ&q=weathering+by+wind&oq=weathering+by+wind&gs_l=img.3..0j0i5i30j0i8i30j0i24.929894.932931..933218...0.0..0.111.1481.17j1......0....1..gws-wiz-img.......0i67.biv2kgpHUHw&safe=active&ssui=on#imgrc=oTGdY3E5LWRhDM:

Chemical Weathering

As rocks break apart, surface area is increased As rocks break apart, surface area is increased. This can accelerate further mechanical weathering, as well as chemical weathering. Remember that increasing surface area speeds up chemical reactions.

Chemical Weathering and Organisms How do living organisms cause chemical weathering? Discuss with your partner and be prepared to share.

How Organisms Contribute to Chemical Weathering As they draw nutrients from their surroundings, lichens produce a weak acid that can dissolve rock. As plant roots expand into rock, acids can change the minerals in the rock. Plant roots also use carbon dioxide, changing the chemistry of the soil. Bat guano (poop) and other animal remains contain reactive chemicals that can affect minerals.

Chemical Weathering – Acids/Carbon dioxide/Dissolution https://www.google.com/search?rlz=1C1GCEV_en&biw=1366&bih=622&tbm=isch&sa=1&ei=BpsOXLT7N5LYsQWZpKAw&q=oxidation+in+rock&oq=oxidation+in+rock&gs_l=img.3..0j0i24.243850.247087..247632...0.0..0.86.1215.17......0....1..gws-wiz-img.......0i67j0i5i30j0i8i30.6wUtjTQBd_I&safe=active&ssui=on

Chemical Weathering - Oxidation

Climate and Mechanical Weathering The two key climate factors that affect the rate of weathering are temperature and moisture. Cold, moist climates are more conducive to physical (mechanical) weathering. The constant cycle of freeze-thaw causes minerals in rocks to expand and contract (thermal expansion and contraction), weakening the surfaces of rocks. Also, water filling cracks in rock expands as it freezes, weakening rock (ice-wedging or frost-wedging). Think about how potholes get worse in the winter. A cold, dry climate will produce the lowest rate of weathering. Without moisture, many of the processes that weather rock will not occur.

Climate and Chemical Weathering The two key climate factors that affect the rate of weathering are temperature and moisture. Warm, wet climates are more conducive to chemical weathering. Remember that the rate of most chemical reactions increases as the temperature increases (you learned this in chemistry). And think about how moisture can speed up chemical reactions, too. Think about the formation of rust. Iron reacts with oxygen to form iron oxide. An old car or bicycle will rust much more quickly if left out in the rain. Also, the warmer a climate is, the more types of vegetation it will have and the greater the rate of biological weathering. This happens because plants and other organisms grow and multiply faster in warmer temperatures.

Climate and Weathering temperature and moisture Rocks can be weathered in any climate. It really depends on the type of rock and the forces at work. But, the general rule is (and don’t forget this): Mechanical weathering occurs at a faster rate in cold, wet climates. Chemical weathering occurs at a faster rate in warm, wet climates.

Erosion The movement of sediment by way of wind, water, ice, and gravity.

Winds carry sand and deposit it, usually in mounds, called dunes.

Alluvial Fans and Deltas

*An alluvial fan is a triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt. This sediment is called alluvium. Alluvial fans are usually created as flowing water interacts with mountains, hills, or the steep walls of canyons. Sediment is deposited at the base of mountain ranges (on land).

Deltas *Deltas are wetlands that form as rivers empty their water and sediment into another body of water, such as an ocean, lake, or another river. As a river nears its end (mouth), it slows in velocity. Suspended sediment falls and creates a triangle-shaped landform called a delta that extends out into another body of water. Deltas are nutrient-rich and support diverse wildlife ecosystems. They absorb run-off and help to filter water, reducing the impact of pollution.

Nile Delta Quick Facts -The planet's longest river, the Nile, has a mouth that forms a famous triangle called the Nile Delta. Most of Egypt's habitable land is within the Nile Delta and along the Nile River. The Nile Delta is one of northern Africa's most fertile regions -- people have farmed it for thousands of years. With an area of around 22,000 square kilometers (8,494 square miles), the Nile Delta is Egypt's main oil and gas producing region. https://sciencing.com/nile-delta-7289614.html

Nile River Delta

Nile River Delta

The Mississippi River Delta region is a 3-million-acre (12,000 km2) area of land that stretches from Vermilion Bay on the west, to the Chandeleur Islands in the Gulf of Mexico on the southeastern coast of Louisiana.[1] It is part of the Louisiana coastal plain, one of the largest areas of coastal wetlands in the United States. The modern Mississippi River Delta formed as the Mississippi River, the largest river in North America, deposited sand, clay and silt along its banks.

Mississippi River Delta

Mississippi River Delta

Effects of Weathering and Erosion Changes in the slopes and texture of rock structures, hills, and valleys Landslides Sinkholes and caves Wearing away of buildings, statues, and roads Soil, pollutants, and other harmful substances from roads and farms washing into waterways Reduction in the area of a beach or shoreline Creation of river deltas and alluvial fans

Let’s review the quiz.

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