CENTENARY SECONDARY SCHOOL
Department of Humanities: Geography Grade 10
Topic: Plate Tectonics 10/08/2020- 14/08/2020
Moving of Continents -Theory of Continental Drift – Pg 54 Study Guide & Pg 153 Textbook
Scientists believe that the Earth was once a single supercontinent called Pangaea. This
continent were split into two called Laurasia in the North and Gondwanaland in the south.
These further split into the Continents as we see them today. This theory was postulated by
Alfred Wegener in 1912. He believes that the polar flight force (attraction of the poles) and
the rotation of the Earth cause the crust to move. Scientists confirm that the continents are
still moving today and estimated such movements at around 2 cm per annum. This theory
forms the basis for the theory of plate tectonics which emerged much later in the 1960's.
Evidence of continental drift
the shapes of the Continents fit together like a jigsaw puzzle. Similar plant and animal fossils
have been found along the coastlines that seemed to fit together in shape. Similar rocks occur
with the same age and structure along the edge of some coastlands. Evidence of different
climates such as glaciers and deserts in areas that don't match. Example: There is evidence
that the equatorial forests were once covered with ice.
The theory of plate tectonics
The Earth's crust is made up of 14 sections called plates. These plates are not stationary. The
theory of plate tectonics explains how and why plates move and also the formation of
volcanoes, earthquakes, oceanic trenches and other geologic phenomena. The rigid crust that
has broken into the plates float on the molten mantle. divided up into a series of plates. These
plates are moving as a result of forces within the mantle.
What are plate tectonics?
As heat rises from the mantle, it deforms the crust and breaks it into large sections which can
move on the mantle. We call these sections tectonic plates. Most tectonic plates carry both
continents and oceans.
The mechanics of plate movements.
Heat inside at provides the energy for the mechanics which causes the plates to move. Heat
rises from the core and spreads through the mantle in convection currents. These currents
form convection cells, so heat is constantly moving towards the crust. At the top of each
convection cell, the convection current moves sideways and eventually downwards to
complete the cell. It may be difficult to believe that the hard, rigid tectonic plates that make
up the Earth’s crust are moving. But below the crust, the mantle has a plastic consistency. In
other words it is not rigid, and so it can move flow. Geologists describe the upper layer of the
mantle, immediately below the plate, as a soft layer of slush. The tectonic plates can just
slowly on this slush.
Figure 2: Movement of plate tectonics
Complete the following activity and return to school when picking up the next
worksheet:
Activity 8 found in the Textbook on Pg 153
or
Activity 2.4 found in the study guide on Pg 66