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The Effects of Weathering & Mechanical Weathering

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by

Johna Pozycki

on 21 April 2014

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Transcript of The Effects of Weathering & Mechanical Weathering

The Effects of Weathering & Mechanical Weathering
Miss Pozycki
What is weathering?
Weathering
is the process that breaks down rock and other substances at Earth's surface.
Forces of Weathering
The forces of weathering
break rocks into smaller and smaller pieces
. Then the forces of
erosion
carry the pieces away.
Mechanical Weathering!
*If you hit a rock hard enough with a hammer, the rock will break into numerous pieces. Some forces of weathering can also break rock into numerous pieces.
Mechanical weathering
is the type of weathering in which a rock is broken into smaller pieces.

These smaller rocks have the same composition, or make up, as the original rock they came from.

If you have ever seen rocks that are cracked or peeling in layers, then YOU HAVE SEEN ROCKS UNDERGOING MECHANICAL WEATHERING!!
The Forces of Mechanical Weathering
Lets refresh our memory....
Freezing and Thawing
In liquid form, water is able to penetrate the many holes, joints, and fissures within a rock. As the temperature drops below 32 ° F, this water freezes. As water
freezes
, it
expands
, becoming about 10%
larger
than it was in liquid form. The result is that the holes and cracks in rocks are pushed outward. Even the strongest rocks are no match for this force.
Release of Pressure
As erosion removes material from the surface of a mass of rock, pressure on the rock is reduced. This release of pressure causes the outside of the rock to crack and flake off like layers of an onion.
Plant Growth
Roots of trees and other plants enter cracks in rocks. As the roots grow, they force the cracks farther apart. Over time, the roots of even small plants can pry apart cracked rocks.
Abrasion
Wind, water, or ice can wear away exposed rock surfaces over a period of time. Sand and other rock particles are then carried away. Imagine rubbing sand paper on wood over a period of time.
What factors contribute to weathering?

Heat
Cold
Water
Ice

Examples of weathering:
wearing down of mountains
bicycles rusting
paint peeling
sidewalks cracking
potholes forming
Erosion-
the movement of rock particles by wind, water, ice, or gravity.
Weathering and erosion work together continuously to wear down and carry away rocks at Earth's surface.
There are TWO types of weathering we will be learning about:
mechanical
and
chemical
. Today, we will focus on....
Mechanical weathering breaks rock into pieces by:
freezing and thawing
release of pressure
growth of plants
actions of animals
abrasion
Mechanical weathering is a
slow
process.


Over long periods of time, it does more than just wear down rocks! Mechanical weathering can wear away
whole mountains
!


1. freezing and thawing
2. release of pressure
3. growth of plants
4. actions of animals
5. abrasion
As the water thaws, it is then able to penetrate further into the widened space, where it later freezes yet again. The expansion of holes and cracks is very slow.
However
, water does not mind. It is very patient. Month after month, year after year, water
freezes and thaws over and over
, creating larger and larger holes and cracks in the rocks.
Review:
Water seeps into cracks in rocks
Temperature drops (below 32° F)
Water expands when frozen
Ice acts like a wedge- a simple machine that forces things apart
Wedges of ice in the rock widen and deepen cracks
Ice melts
Water seeps deeper
Freeze and thaw process repeats!

Animal Actions
Animals that burrow in the ground-- including moles, gophers, prairie dogs, and some insects- loosen and break apart rocks in the soil.
Some animals, such as lichens and mosses can squeeze into cracks and crevices, where they take root. As they grow, so do the cracks, eventually splitting into bits and pieces.
Full transcript