Weathering Soil and Wasting Unit 7 notes Weathering

Weathering, Soil, and Wasting Unit 7 notes

Weathering �What is it? ◦ Disintegration and Decomposition of rocks �Where does it happen? ◦ At or near the surface of the Earth

Weathering �What does this process look like?

Weathering �Why does it happen? ◦ It is the response of Earth’s materials to the changing environment.

Weathering �How many types are there? ◦ Mechanical ◦ Chemical

Weathering- Mechanical �A physical process �Rocks are broken into smaller and smaller pieces, each retaining the characteristics of the original (parent) material

Weathering- Mechanical �Frost Wedging ◦ Water enters and fills cracks in the rock. It will expand when the water freezes and push the rock apart more.

Weathering- Mechanical �Talus Slopes ◦ The pile of rocks that forms at the base of a vertical rock formation. Most often the result of frost wedging.

Weathering- Mechanical �Unloading ◦ Large scale loss of rocks off of the original parent material

Weathering- Mechanical �Sheeting is also known as exfoliation. ◦ What is exfoliation on people?

Weathering- Mechanical �Sheeting- ◦ When large masses of rock (particularly igneous) are exposed and large flat pieces are broken off due to a reduction in pressure

Weathering- Mechanical �Thermal Expansion ◦ What happens when you heat something up? ◦ Cool something down?

Weathering- Mechanical �Biological activity ◦ Plants, animals (including humans), lichens, mosses ◦ Plant roots will wedge in between rocks to seek water. Lichens will actually digest the surface of rocks for nutrients. And humans will do what we do…

Weathering- Chemical �Carbonic Acid- ◦ H 2 CO 3 is produced when CO 2 dissolves in H 2 O. ◦ Water vapor in the air undergoes this reaction.

Weathering- Chemical �How carbonic acid works on Feldspar… ◦ 2 KAl. Si 3 O 8 + 2 H 2 CO 3 + H 20 Al 2 Si 2 O 5(OH)4 + 2 KHCO 3 + 4 Si. O 2 ◦ What it looks like…

Weathering- Chemical �Rocks that undergo this process tend to take on a spherical shape.

Soil �“Science, in recent years , has focused more and more on the Earth as a planet, one that for all we know is unique-where a thin blanket of air, a thinner film of water and the thinnest veneer of soil combine to support a web of life of wondrous diversity in continuous change. ” ◦ Jack Eddy 1993

Soil �Regolith ◦ The surface layer of the Earth that is composed only of weathered rock and mineral fragments

Soil �What is it? ◦ A combination of weathered mineral particles, organic matter, water, and air �What makes for good soil? ◦ A mixture of approximately 50% regolith and 50% humus (decayed organic material)

Soil �This is where erosion fits into the mix.

Soil �As materials are eroded, certain minerals and elements can be left behind or concentrated to form ore and mineral deposits.

Mass Wasting �Large movements of rock and/or soil in a downhill direction

Mass Wasting �Triggers of mass wasting ◦ Water saturation

Mass Wasting �Triggers of mass wasting ◦ Oversteepened slopes

Mass Wasting �Triggers of mass wasting ◦ Vegetation- or rather removal of vegetation

Mass Wasting �Triggers of mass wasting ◦ Earthquakes