Earth’s Land
Part One – Shaping the Land
The land on our Earth is constantly changing. Some of these changes
happen quickly – like a volcano erupting or an earthquake. Other
changes take many years – like the creation of a mountain or a valley.
Two important processes that shape the land are called weathering and
erosion.
Weathering happens when rock is
broken into smaller pieces. This can
happen when a chemical change takes
place in the rock, like when the air
dissolves minerals in the rocks.
Weathering can also take place when
water or plant roots, or freezing and
thawing, weaken the rock.
Erosion happens when rocks are broken
down and carried from one place to
another by moving water or ice, or by the
wind. Moving water causes the most
erosion.
Erosion can be caused by a river system. The rainwater, brooks and
streams that come together to form a river are called a river system.
The moving water of a river system caries soil, sand, gravel and rocks.
The material moved by water is called sediment.
When the river reaches the ocean, the fast-moving water slows down.
The water is no longer moving fast enough to carry the sediment. As the
water slows down, the sediment is dropped where the river meets the
ocean. The sediment forms a flat plain called a delta.
Earth’s Land
Part Two – Water Changes the Shoreline
There are many ways that the ocean can
change the shape of the land. Waves from
the ocean can also move sediment and
deposit it on the shoreline. This is how
beaches are created. Beaches can have
different kinds of sand depending on the
sediment that the ocean is moving.
Some water from the ocean forms a bay. A bay is a part of the ocean
that extends into the land. It is mostly surrounded by land, but has an
opening to the ocean.
Sometimes a
natural part of
the land
extends into
the water –
this is called a
headland. The headland blocks the flow of
water, which changes where sediment is
deposited. This is one way the shape of the
shoreline can change.
Earth’s Land
Part Three – Wind Shapes the Land
Wind can change the shape of the
land through erosion or weathering.
Wind can move sand and dirt from
one place to another. Windblown
sediment can move along the ground
like a sandblaster, chipping away at the earth or polishing it.
Wind can also build up the land by depositing sediment in one
place. Sand dunes are formed when wind deposits sands in the
shape of a mound, hill or ridge.
Erosion and weathering by the wind takes more time than
erosion or weathering by water. This is because wind is not as
powerful as moving water.
Earth’s Land
Part Four – Glaciers
A glacier is a huge mass of moving ice that forms over land.
Glaciers are formed in cold areas where the snow never
completely melts. The snow piles up, becomes heavy, and turns
into ice. Eventually a glacier forms.
Glaciers are very heavy, and their weight causes them to move
outward from the center. Glaciers move very slowly, but their
great weight casus the land underneath them to change.
Glaciers also carry sediment, so glaciers can change the land by
moving and depositing sediment. The sediment moved by a
glacier is much larger and heavier than the sediment moved by
wind or water.
Glaciers can form the land into valleys, peaks, ridges, cliffs,
lakes and waterfalls. They can shape mountains and leave huge
boulders and piles of rocks in their path.
Look at the following pictures. Describe how a glacier changed
the land in each picture.