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World Geography 3202
Unit One
Land And Water Forms
Introduction
• Unit 1 introduces You to the concept that the earth’s surface is
shaped by building-up and wearing away forces.
• The unit will help You to examine the constituent parts of the physical
environment, forces that created them, patterns in their distribution,
and how they influence selected human activities.
Patterns in the location of landforms on the
earth’s surface
Q#1 What category of landforms
would be reflected in this type of
diagram
Q#2 What pattern can be seen
from the diagram of landforms
illustrated here?
Relief map of North America
Q#1 How would you describe the distribution of
landforms illustrated in this map?
Q#2 What type of landforms can you identify on
this map?
Q#3 Where in the Americas are you most likely
to encounter:
Mountains
Large Lakes
Plains and Plateaus
Large Rivers
River Deltas
Questions for Review
• Define the term topography.
• Differentiate among the terms hill and mountain, and
plain and plateau.
• Identify: seismology; minerals; rocks; compounds;
elements; Igneous rocks; Sedimentary rocks;
metamorphic rocks; Valleys;
• Describe the distribution of these landforms over the
earth’s surface
How did this distribution come about?
• The earth’s landforms are never static: That is to say, they are
constantly in a state of change due to forces at work that both wear
down the land, as well as build up and shape the land.
• First, we are going to look at forces that build up and shape
landforms,….
Forces that shape the earth’s land formations
• The face of the earth is shaped by tectonic activity.
• Tectonic activity can be described as the movement of the earth’s
crust, or “plates” as a result of the pull of gravity; convection currents,
or the circulating movement of fluid rocky material in the mantle; and
thermal plumes, or vertical columns of molten rocky material in the
mantle.
Crustal Movement Under the ocean
How Plate Tectonics Explains the shaping of
landforms
• The theory of plate tectonics was formulated during the early 1960s,
and it revolutionized the field of geology.
• Scientists have successfully used it to explain many geological events,
such as earthquakes and volcanic eruptions as well as mountain
building and the formation of the oceans and continents.
What are Tectonic Plates?
• Tectonic plates are made of either oceanic or
continental crust and the very top part of the mantle,
a layer of rock inside the earth.
• This crust and upper mantle form what is called the
lithosphere.
• Under the lithosphere lies a fluid rock layer called the
asthenosphere.
• The rocks in the asthenosphere move in a fluid
manner because of the high temperatures and
pressures found there.
• Tectonic plates are able to float upon the fluid
asthenosphere because they are made of rigid
lithosphere.
Layers Of the Earth
1.Mantle
2.Lithosphere
3. Outer Core
4. Inner Core
How compressional forces are caused.
• Compressional /
Destructive (subduction
zones) plate boundaries
occur when an oceanic
plate is forced under (or
subducts) a continental
plate
• What do you think could
be the result of this type
of force?
Compression at Work:
How tensional forces are caused
• Tensional / Constructive
(divergent ) plate
boundaries occur when
two plates move away
from each other
• What do you think could
be the result of this type
of force?
Relate selected plate movements to compressional and
tensional forces
• An earthquake is a sudden movement of the earth's surface.
• Earthquakes are caused by the movement of the earth's tectonic
plates.
• Earthquakes occur where the earth's plates meet along plate boundaries
An example of the cause of an Earthquake
• For example as two plates move towards each other, one can
be pushed down under the other one into the mantle.
• If this plate gets stuck it causes a lot of pressure on
surrounding rocks.
• When this pressure is released it produces shock waves.
These are called seismic waves. This is an earthquake.
• The waves spread out from the point where the earthquake
started - the focus. More damage is done near the focus.
• The point on the earth's surface directly above the focus is
the epicentre.
Volcanoes
• A volcano is a conical hill or mountain formed by
material from the mantle being forced through an
opening or vent in the Earth's crust.
Volcanoes are found in three states - extinct, dormant
and active.
• An extinct volcano will never erupt again.
• A dormant volcano has not erupted in 2000 years.
• An active volcano has erupted recently and is likely to erupt
again.
• Volcanoes are found along destructive (subducting)
plate boundaries, constructive (divergent) plate
boundaries and at hot spots in the earth's surface.