The Earth’s Crust

Weathering & Erosion

!  Soil begins with rocks – so how is rock turned into soil?

!  How does soil travel and move?

!  Without sediments our planet 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 oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). 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 crystal 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 wind, water and ice

There are two main kinds of weathering:

!  1. Mechanical !  2. Chemical

! Mechanical Weathering– the physical break up of rocks.

Examples ! 1.Gravity –

pulls rocks down cliffs and mountains 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, rivers, glaciers, ocean 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 regolith.

!   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 land. 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. Landslides 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 lichen 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. !  Acid rain dissolves minerals found in rock which weakens the entire rock making it easier to break. !  It occurs because rainwater mixes with carbon dioxide in the atmosphere, forming a weak carbonic acid.

George Washington, New York 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.

Acid rain contains carbonic, nitric and sulfuric acid, that are produced by oxidation and dissolution in water of gaseous oxides (CO2, NO2 and SO2), present in the air as chemical pollutants.

A Karst Limestone 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 Sulfur Dioxide (SO2) -81 -79 -70 www.epa.gov

Other Chemical damage