Geography Essentials - Earth & Plate Boundaries

Earth & Plate Boundaries

This O level Geography course covers the topic on Sec 3 Plate Tectonics - Earth and Tectonic Plates from the O level syllabus 2022. Firmin, our Geography tutor, will build your understanding on this physical geography topic. The focus of this course is on understanding the structure of the earth, different types of plate boundaries, as well as tectonic plates movement.

The geography notes are designed to be a useful companion with case studies and contain practice questions of various difficulty for you to strengthen your understanding of the concepts. Firmin will guide you on the answering techniques for these practice questions.

In this course, we will uncover the following topics:
✦ Earth and tectonic plates
✦ Plate boundaries and resultant landforms

This course is suitable for pure geography and elective geography students of all levels.

Example:
The Movement of Tectonic Plates
The earth’s tectonic plates are always moving because of the convection currents and the slab-pull force in the mantle.

Fig. 2.1 shows the process of how convection currents and slab-pull force work together to cause plates to move.

Fig 2.1


✦ Convection Currents

When the molten magma is heated, it expands, rises and becomes less dense as compared to the cooler, upper magma, which then sinks. This process creates the convection currents.
(1): When the rising warmer magma reaches the crust above, it spreads out beneath the crust and pushes the plates away from each other.
(2): As it cools, it sinks down to be reheated and brings the plates towards each other.
(3): This continuous rising and sinking of the magma causes the plate to move over the Earth’s surface.
Slab-pull force is a result of convection currents causing plates to converge.
(4): Slab-pull force occurs when the dense, sinking denser plate at subduction zones pulls the remains of the plate behind it. This is currently thought to be the main driving mechanism for plate movement.
(5): The subducting, or sinking, plate drives the downward moving portion of convection currents.
(6): The mantle material, which is found away from where the plates subduct, drives the rising portion of convection currents.

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