Mechanical and chemical forces break down rock

1
Mechanical and chemical forces break down rock

• When you are walking in your neighborhood how do
  you think the small rocks are formed?

2
Mechanical and chemical forces break down rock

• Weathering, which is the process by which natural
  forces break down rock.

3
Mechanical and chemical forces break down rock

• There are two ways in which weathering can occur.
• Physically broken apart and chemically

4
Mechanical and chemical forces break down rock

• Mechanical weathering breaks up rock by physical
  forces.
• Those physical forces split apart rock
• Mechanical weathering can be caused by ice
  wedging, pressure release, plant root growth, and
  abrasion.

5
Mechanical and chemical forces break down rock

• Ice wedging causes mechanical weathering. When
  water freezes in the cracks and pores of rocks,
  the force of its expansion is strong enough to
  split apart rock.

6
Mechanical and chemical forces break down rock

• Pressure release is the next method. Rock deep
  within the earths surface is under great amounts
  of pressure. Over time the rock is pushed up to
  the surface of the earth.

7
Mechanical and chemical forces break down rock

• When the rock reaches the surface the pressure is
  released and the rock expands. As the rock
  expands cracks from in it causing weathering.

8
Mechanical and chemical forces break down rock

• Plant Root growth is method in mechanical
  weathering. When plants grow in a rock, their
  roots can widen the crack and force the rock
  apart. Thus mechanical weathering takes place.

9
Mechanical and chemical forces break down rock

• Abrasion is the final method in mechanical
  weathering. Water alone can wear down rocks, but
  they also can move rocks downstream causing them
  to rub together and wear down into rounded
  shapes.

10
Mechanical and chemical forces break down rock

• When elements react with water and air they can
  cause the breakdown of rocks. This is of course
  chemical weathering.

11
Mechanical and chemical forces break down rock

• When minerals in rocks come into contact with air
  and water, some dissolve and others react and are
  changed into different minerals.

12
Mechanical and chemical forces break down rock

• Water is the main cause of chemical weathering.
• Water and carbon dioxide mix with decaying plants
  and breaks down rock into smaller pieces.

13
Mechanical and chemical forces break down rock

• Oxygen is also a major factor in chemical
  weathering.
• When minerals dissolve in water, oxygen in the
  air and water combines with iron to produce iron
  oxides or rust.

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Mechanical and chemical forces break down rock

• Just like the rock cycle weathering can take
  hundreds, thousands, or millions of years.
• The surface of the earth will weather at a faster
  rate because of the exposure to air and water.

15
Mechanical and chemical forces break down rock

• Different rocks break down at different rates
  such as limestone and granite.
• Climate can also affect chemical weathering.
• Weathering occurs faster in hot wet regions than
  cold dry regions. Why?

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Mechanical and chemical forces break down rock

• Although mechanical weathering can occur more in
  cold regions rather than hot. Why?