Weathering and Erosion pull out your HW

HW 14-1 #1-7 wind, water, and temperature change Water that seeps into cracks freezes and expands, which widens and deepens crack with each freeze/thaw cycle. Plant roots grow and expand, physically wedging rocks apart. Animal dig and burrow, which exposes new rock to weathering. Mechanical weathering is a physical process, breaking large rocks into smaller rocks of the same chemical composition. Chemical weathering involves chemical reactions.

In oxidation, iron bearing minerals combine with oxygen to form red colored iron oxide. In hydrolysis, water and other substances in rock react chemically to form two or more new substances. In carbonation, carbonic acid converts minerals into carbonates. Oxidation, hydrolysis, and carbonation are all chemical processes that weather rocks. Acid precipitation forms when nitrogen oxides and sulfur dioxide released during fossil fuel combustion combine with water in the atmosphere to produce nitric, nitrous or sulfuric acid. When these acids fall back to earth they called acid precipitation.

Weathering The breakdown of rocks on Earth’s crust into smaller pieces. How did this rock get to look like this? PREDICT.

Mechanical (Physical) Weathering Process by which rocks are broken down into smaller pieces by external conditions. Types of Physical weathering Frost heaving and Frost wedging (ice) Plant roots Friction and impact Burrowing of animals Temperature changes

Frost Wedging

Frost Heaving

Plant Roots

Friction and Repeated Impact

Burrowing of Animals

Temperature Changes

Mechanical Exfoliation is the peeling off of sheets of rock as they expand and crack.

Chemical Weathering The process that breaks down rock through chemical changes. The agents of chemical weathering Water (Dissolution) Oxygen (Oxidation) Carbon dioxide (Carbonation) Living organisms Acid rain

Water: Dissolution Water weathers rock by dissolving it

Oxygen: Oxidation Iron combines with oxygen in the presence of water in a processes called oxidation The product of oxidation is rust

Carbon Dioxide CO2 dissolves in rain water and creates carbonic acid Carbonic acid easily weathers limestone and marble

Living Organisms Lichens that grow on rocks produce weak acids that chemically weather rock

Acid Rain Compounds from burning coal, oil and gas react chemically with water forming acids. Acid rain causes very rapid chemical weathering

Chemical Weathering

Karst Topography A type of landscape in rainy regions where there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams. Created by chemical weathering of limestone

Features of Karst: Sinkholes

Features of Karst: Caves

Features of Karst: Disappearing Streams

Transport Agent of Forces Water Wind Ice (glaciers) Gravity

Transport Agents - Water Rain Streams and rivers Ocean dynamics Ice (glaciers)

Streams

Stream Erosion and Deposition

Glaciers

Wind Transport of Dust

More Wind Transport of Dust – West Coast of Africa

Deposition Formation

Deposition Formation

Erosion The process by which water, ice, wind or gravity moves fragments of rock and soil.

Water Erosion Rivers, streams, and runoff

Ice Erosion Glaciers

Wind Erosion

Mass Movements Landslides, mudslides, slump and creep landslide clip.mpeg

Quiz Time – List weathering, erosion, both or neither 1.Waves are crashing on a sand beach. 2.Water expands as it freezes in the cracks of rocks. 3. Pebbles move down a stream with the current.

4. Acid rain causes the decomposition of a statue in New York. 5. A Glacier slowly moves down a mountain. 6. A tree’s roots grow into the cracks of rocks. 7. A major volcano erupts

9. A shovel is left outside and begins to rust.

1. As the sand is moving there is definitely erosion; there is also abrasion from the sand gains colliding. Both

2. This is frost wedging so it’s mechanical weathering 2. This is frost wedging so it’s mechanical weathering. There is no mention of movement. Weathering

3. There is probably some weathering, but there is definitely erosion 3. There is probably some weathering, but there is definitely erosion. Erosion or Both

4. Acid rain on a statue is chemical weathering 4. Acid rain on a statue is chemical weathering. This is mainly Weathering.

5. A glacier moving down a mountain would have both weathering and erosion. Both

6. A tree’s roots growing into cracks of rocks would be weathering 6. A tree’s roots growing into cracks of rocks would be weathering. Weathering 7. A tree’s roots growing into cracks of rocks would be weathering. Weathering

7. A major volcanic eruption would involve both weathering and erosion 7. A major volcanic eruption would involve both weathering and erosion. Both

8. The rusting of a shovel is oxidation. This is chemical weathering 8. The rusting of a shovel is oxidation. This is chemical weathering. Weathering

Vocabulary: Differential Weathering Surface area Climate topography 14-2 Rates of Weathering Vocabulary: Differential Weathering Surface area Climate topography

Weathering Is a SLOW destructive process. Carbonation weathers limestone one-twentieth of a cm (0.002) every 100 years. Math Practice in 14-1: Limestone is dissolved by chemical weathering at a rate of 0.2 cm every 100 years. At this rate, after how many years would a layer of limestone 15 m thick completely dissolve?

1. Composition Differential Weathering: the process by which softer, less weather resistant rocks wear away at a faster rate than harder, more weather resistant rocks do Sedimentary rocks (like limestone) weather rapidly compared to other type

2. Amount of Exposure The more exposure to the weathering agents: wind, water, gravity, the faster the rock will weather. Surface Area: as rocks break into smaller pieces the surface area increases therefore weathering rate increases Lab Demo: Sugar cube crushed up and sugar cube not crushed up. Volunteers to stir. Same temperature of water. Hypothesize, which will dissolve quicker? Analysis: What does amount of exposure/surface area have to do with time it takes to “weather”.

3. Climate Alternating hot/cold climates tend to weather faster because of the freezing and thawing cycle, causing frost wedging a form of mechanical weathering.

4. Topography The elevation and slope of the land surface Temperatures are generally colder higher up in elevation frost wedging is more evident. The steeper the slope, the more rocks pulled downhill by gravity

5. Human Activities Mining, construction, recreational activities, etc. View Mining Video (22 minutes)

6. Plant and Animal Activities