Chapter 6 Objectives:
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Geography 12 Key
Worksheet 6.1
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The Lithosphere In Motion: Plate Tectonics
Read pages 86 – 88 of Planet Earth: A Physical Geography. Answer
the following questions:
Vocabulary (1 mark each)
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Plate: a rigid slab of solid lithosphere rock that has defined boundaries
and floats on the denser rocks of the asthenosphere
Asthenosphere: the plastic (part solid, part liquid) layer of the upper
mantle directly below the lithosphere that can flow slowly when put
under constant pressure.
Tectonics: the processes that deform the earth’s lithosphere and the rock
structures and surface features created by these processes.
Lithosphere: the solid outer layer of the earth where the rocks are less
dense and more rigid than those of the asthenosphere below; includes
the top part of the mantle and all of the crust.
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Appreciate the power and
scope of tectonic processes
and their effects
Appreciate the slowness of
tectonic processes based on
a human time scale
Understand that the
lithosphere is an everchanging part of a
dynamic planet
Understand the general
pattern of tectonic activity
over geologic time and
explain the location pattern
of tectonic activity over the
earth’s surface
Explain the tectonic
processes that shape the
earth’s surface, including
folding, faulting, and
volcanic activity
Describe and explain the
pattern of major surface
features created by tectonic
processes
Predict the nature and
general patterns of
occurrence of tectonic
activities and processes,
especially earthquakes and
volcanic eruptions
Describe the positive and
negative aspects of tectonic
activities
Short Answer (2 marks each)
1. Explain what a plate is.
A rigid slab of solid lithosphere rock that has clearly defined boundaries. It is
big…often as big as continents.
2. Where is the asthenosphere and why do scientists consider it plastic?
It is the layer of the upper mantle directly below the lithosphere. It is considered plastic
because it is part solid, part liquid ad can flow under pressure.
3. What sets the plates in motion? Describe the process.
Convention currents (heat rising) in the asthenosphere expand and migrate to the
surface while cooler material flows to fill the void.
4. Draw, scan, or retrieve a picture from the internet that shows convection currents
in the asthenosphere and how they may move solid lithospheric rock.
5. Explain why the plastic nature of the asthenosphere and the presence of
convection currents are key elements in the theory of plate tectonics.