Transcript Forces That Shape Our Earth

Forces That Shape Our Earth:
Erosion and
Weathering
Why is this important?
1. Erosion and weathering are major forces
that shape the world around us.
Understanding these forces helps us to
understand the way our land is shaped –
from rivers to lakes to canyons and our
shore lines. For example the Grand
Canyon was formed through erosion by
the Colorado River running through it!
Why is this important?
2. People play a part in the way and
amount that our soil erodes around us. It is
important for us to understand how
erosion works and how effect on soil
erosion since we depend on soil to grow
our food and without it we would starve!
So what is erosion?
Erosion:
when earth’s
surface is
worn away.
Erosion is caused by
moving water, oceans,
wind, and the glaciers.
Soil Erosion
When we think about erosion we usually
think about our soil being worn away and
moving around. This is important to
humans because we need soil to grow our
food.
Plant roots help soil stay where it is
supposed to and humans can make soil
erosion worse by cutting down our trees.
Apple Demonstration
(1) Cut a large apple into four equal parts. "Three parts represent the oceans
of the world. The fourth part represents the land area of the world."
(2) Cut the land section in half lengthwise. "One section represents land such
as deserts, swamps, antarctic, arctic, and mountain regions. The other 1/8
represents land where man can live but may NOT grow food."
(3) Slice this 1/8 section crosswise into four equal parts. "Three of these 1/32
sections represent the areas of the world which are too rocky, too wet, too
hot, or where soils are too poor for food production, as well as areas
developed by man."
(4) Carefully peel the last 1/32 section. "This one small bit of peeling
represents the soil of our earth on which mankind depends for food
production."
Weathering
One type of erosion is
when rocks are broken
down. We call this
weathering.
So what is weathering?
Weathering: The breaking down
of rocks into smaller pieces.
Hulk
Rock
Smash!
Add to your vocab book
There are five types of
weathering…
Add this to your vocab book
Five types
of weathering
Wind
Wind breaks down rocks in two ways:
1. Wind can blow small pieces of rock off
a large rock.
2. Wind blows sand, which grinds pieces
of rock off a large rock.
Plant Roots
Plants roots can grow into
cracks in the rock, slowing
breaking them apart.
Freezing Water
In your groups, hypothesize how the water
in this rock can cause weathering. (Hint:
what happens to water when it freezes?)
Flowing Water
Water changes the landscape as it
flows, or moves, by moving rocks
and soil as it goes.
Moving water is THE STRONGEST
weathering force changes the
land we see.
Chemical Weathering
This is when an acid that
either occurs natural or
because of pollution (acid
rain) breaks down rocks.
One more thing we need to
know….
Deposition
After the earth’s surface has eroded or the
rocks are weathered, these materials
move. When they stop moving and are
“dropped off” we call this deposition.
Deposition: when soil and rocks are
deposited, or left, somewhere different
then where they started.
(Add to your vocab book)
Quiz on Monday!! Don’t
forget to learn and study
your new (and old)
vocabulary words!!