Download Changes in Earth`s Surface

Changes in Earth’s Surface
Essential Questions and Answers:
What are constructive processes?
Constructive forces affect the earth's surface by building
it up while forming new crust and landforms like
mountains, islands, deltas, and sand dunes.
What are destructive processes?
Destructive forces affect the earth's surface by breaking
down landforms to form new ones through the processes
of weathering and erosion.
How do constructive and destructive processes affect
the surface features of the Earth?
Earth’s crust is forever changing. The continents and ocean floors are part of Earth’s crust, which is
broken into big pieces called plates. These giant plates float and move on top of the mantle. The areas
where the plates meet are called boundaries. As the plates of the crust move, they can collide and form
mountain chains. They can pull away from each other and form new crust along the ocean floor. They
can also slide past each other and cause earthquakes. Earthquakes and volcanoes are often found along
these boundaries, as are mountain chains that formed when the boundaries collided.
Even as constructive forces are creating landforms on Earth, destructive forces are wearing them down.
Weathering and erosion are two forces that are constantly acting to reshape the land. Weathering is
the breaking down of the materials of Earth’s crust into smaller pieces. Erosion is the picking up and
carrying away of the pieces. However, as these eroded pieces of rocks are carried along by wind,
moving ice, or moving water, they eventually stop and are dropped to the bottom of the stream, lake, or
ocean. The dropping off of bits of eroded rock is called deposition. This process helps to build up
Earth’s surface by filling in depressions, or basins. Deposition also causes new sedimentary rocks to
form, as well as new landforms including sand dunes and deltas.
Quick Reference of Constructive and Destructive Forces
Forces
Destructive
Deposition
Constructive
Both
X
Earthquakes
X
Volcanoes
X
Faults
X
Erosion
X
Weathering
X
What are the differences between chemical weathering and physical weathering?
Chemical weathering involves the breakdown of rock by chemical reaction. Chemical weathering turns
the rock from one substance into another. For example chemical weathering in the form of acid rain can
easily break down sedimentary rock like limestone.
Mechanical weathering involves the breakdown of rock by physical means including pounding, grinding,
and cracking. Agents of physical weathering include water, wind, gravity – even plants and animals. As
water freezes, it expands. For example, because water expands as it freezes, rainwater that collects in
the cracks of rocks can break apart the rocks when it freezes.
How does erosion occur?
Erosion is the process whereby small pieces of soil, rock, and other material are carried by wind or water
from one place to another. Rivers and streams often carry large amounts of silt and sand to larger
bodies of water (lakes and oceans) where the debris is deposited. As particles settle out, they form new
land. In the case of river delta, deposition creates new land along a coastline.
What role has technology and human intervention had in controlling constructive and destructive
processes?
1. Seismology- Although we can’t control the constructive and destructive forces caused by
volcanoes and earthquakes, we can monitor them with the use of seismographs. Preparing for
these events can control the amount of damage that occurs.
2. Dams are built across rivers to control the flow of running water. This helps to manage the
destructive force of water erosion.
3. Levees are features along the sides of river that help to contain the flow of water. Rivers
naturally create their own levees through the process of deposition. However, during flooding
periods natural levees may not be strong enough to contain the water, and man-made levees
must be added. These levees are often made of sandbags or concrete. They help to control the
destructive force of water erosion.
Storm-Drainage systems are built along the streets to collect rain water that does not get into the soil.
The water flows through a series of pipes until it is released into a large body of water. They help to
control the destructive force of water erosion.
Essential Vocabulary:
Weathering
Erosion
Fault
Crust
Lava
Volcano
Earthquake
Deposition
Sediment
Landform
Seismograph
Delta
Sand dune
Flood
Dam
Levee
Storm drain