Surface Forces That Shape Earth Flashcards
What forces worn the earth away
Wind, rain, frost and waves
give examples of natural processes that shape all natural landforms
- Rivers carve out valleys and in some places, they leave fertile mud over wide areas.
- The action of waves produces cliffs and beaches along the coast.
- Water and ice break up rocks in high areas, creating pointed mountain peaks.
- In very cold climates, thick layers of ice move over the land, carving deep valleys with steep sides.
- Winds blow sand across deserts, producing sand dunes and sand-carved rocks.
how do people contribute to the shape of the land?
by building settlements, mining rocks, and farming.
define weathering
wearing away of rocks and soil by the action of the weather
define agents
natural forces that cause an effect or result
what does weathering affect
the shape and composition of rocks and soil
what are the most important agents of weathering
temperature and water
what are the three main types of weathering
- Physical weathering
- Chemical weathering
- Biological weathering
what are the causes of physical weathering
physical forces such as frost and temperature changes
what are the causes of chemical weathering
chemical changes that weaken rocks
what are the causes of biological weathering
the action of plants and animals
Compared to a human lifetime, weathering is a slow process. weathering can cause many changes to a landscape
define exfoliation
the removal of the outer layers of a rock after repeated contraction and expansion
what are two examples of physical weathering
freeze thaw action and exfoliation
when does freeze-thaw happen
when water collects in cracks in rocks.
(some cracks may be very small and only contain a few drops of water. other cracks may be much bigger)
what happens when water freezes
it expands. as the water turns into ice it increases its volume and puts pressure on the sides of the cracks
go through diagram on free-thaw action on pg 57
what do big temperature changes during the day and night cause
the outer layers of rocks to expand in the heat of the day and contract with the cooler night.
the constant expanding and contracting weakens the outer layers of rocks; large pieces can ‘peel’ off the outer surface.
Define dissolved
Has become part of a liquid solution
Define insoluble
Does not dissolve in water
Define soluble
Dissolves in water
How can underground caves form
When carbonic acid attacks and dissolves away rocks under the ground.
What does chemical weathering change
The chemical composition of rocks. It weakens rocks, causing them to break up
Give three examples of chemical weathering
Carbonation
Hydrolysis
Oxidation
Read through carbonation on pg 58
Where does oxidation occur
To rocks and objects that contain iron
How can we see oxidation
As rust, on metals that have been left in the rain
What colour are oxidation stains
Red
How does iron oxide form
Water contains oxygen that mixes with the iron content of rocks to form iron oxide
What does oxidation change
The chemical structure of the rock, making it weaker and more easy broken down
What is hydrolysis
A sequence of chemical reactions that involve water, and minerals called silicates
Where are silicates present
In many different kinds of rock including sandstone and granite