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Home , Crust (geology), Weathering

The ’s Crust

Weathering & begins with rocks – so how is turned into soil? How does soil travel and move? Without our would decline, perhaps ceasing to exist

Inside the Earth The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the () and about 25 miles (32 kilometers) thick under the (). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust Three Laws of Thermodynamics

The first law of thermodynamics, also called conservation of energy, states that the total amount of energy in the universe is constant. This means that all of the energy has to end up somewhere, either in the original form or in a different from. We can use this knowledge to determine the amount of energy in a system, the amount lost as waste heat, and the efficiency of the system.

The second law of thermodynamics states that the disorder in the universe always increases. After cleaning your room, it always has a tendency to become messy again. This is a result of the second law. As the disorder in the universe increases, the energy is transformed into less usable forms. Thus, the efficiency of any process will always be less than 100%.

The third law of thermodynamics tells us that all molecular movement stops at a temperature we call absolute zero, or 0 Kelvin (-273oC). Since temperature is a measure of molecular movement, there can be no temperature lower than absolute zero. At this temperature, a perfect has no disorder. When put together, these laws state that a concentrated energy supply must be used to accomplish useful work. Weathering & Erosion

Weathering – a natural process that breaks down and wears away rocks to create sediments Erosion is the movement of small rock particles by , and There are two main kinds of weathering: 1. Mechanical 2. Chemical

Mechanical Weathering– the physical break up of rocks.

Examples 1. – pulls rocks down cliffs and smashing them Moments before this rock fell, it was one large rock. How many pieces of rock do you think there are now?

2.ICE– the freezing and thawing of water within cracks in rocks Freeze-Thaw Action What do you think will happen to this rock when it falls? This rock froze and thawed so many times that it slowly burst from the strain. 3. Erosion– wind, water, and ice wear away at the surfaces of rock and carry the pieces to another spot. E.g. dust storms, , , waves Mass Movement

Mass movement means the movement of any loose material (rocks, soil, mud) down slope under the influence of gravity.

The loose material is known as .

The rate of mass movement is influenced by 4 factors.

• Gradient • Water Content • Human Activity • Vegetation Influences on Mass Movement

Gradient – Mass movement occurs on sloping . Mass movement is fastest on steep slopes.

Water Content – After heavy rain the regolith (loose material) is heavier.

Human Activity – People often cut into hillsides to make roads or railway lines. This creates steep slopes where mass movement can occur.

Vegetation – The roots of trees and plants help keep the regolith together, slowing down mass movement. Types of Mass Movement

There are different types of mass movement. They are grouped according to the speed at which they occur.

Types of Mass Movement

Speed – Slow Speed – Fast

1. Soil Creep 1. 2. Bog bursts 3. Mudflows Soil Creep Soil Creep Landslides Mudflows 4. Biological Weathering – the breakdown of rock by living organisms (plants, fungi, and bacteria) The roots of plants can work their way into the cracks of rocks and widen them while other plants and animals produce chemicals that can erode rock. These are beginning to break down this rock – the first step in a long process of creating soil. How long do you think it takes for soil to form from solid rock? Even these mushrooms break down rock – they secrete digestive juices onto the forest floor and then absorb the nutrients – the acids also inadvertently dissolve small rocks.

Chemical Weathering the breakdown of rocks by water, chemicals, and gasses Chemical reactions can speed up the process of erosion – e.g. . Acid rain dissolves found in rock which weakens the entire rock making it easier to break. It occurs because rainwater mixes with in the , forming a weak . Acid rain contains carbonic, nitric and , that are produced by oxidation and dissolution in water of gaseous oxides (CO2, NO2 and SO2), present in the air as chemical George Washington, New York pollutants. This statue of George Washington was first put outside in New York City in 1944. During the next 58 years, acid rain caused significant damage to the statue.

A Pavement Acid Rain Effects Clean Air Act of 1963

Percent Change in Emissions

1980 vs 2014 1990 vs 2014 2000 vs 2014

Carbon Monoxide (CO) -69 -62 -46 Lead (Pb) -99 -80 -50 Nitrogen Oxides (NOx) -55 -51 -45 Volatile Organic Compounds (VOC) -53 -38 -16 Direct PM10 -58 -19 -16 Direct PM2.5 --- -25 -33 Dioxide (SO2) -81 -79 -70 www.epa.gov Other Chemical damage