Transcript Guided Notes on the Causes of Plate Motions

Guided Notes on the
Causes of Plate Motions
Chapter 17, Section 4
1. What is the leading hypothesis
as to the cause of plate tectonics?
 Large-scale
motion in the mantle is
the mechanism that drives the
movement of the tectonic plates.
 This motion is created by the heat of
the core moving throughout the
mantle in convection currents.
2. Describe in detail how a
convection current occurs.
The heating of matter causes it to expand
and become less dense. This warm
matter rises and forces cooler matter to
sink because of gravity. This matter is
then warmed and rises, which causes
other matter to cool and sink.
 The cycle continues….

3. How do convection currents
cause plate tectonics?
 Convection
currents in the mantle are
set in motion by the transfer of
energy between the Earth’s hot
interior (core) and cooler exterior
(upper mantle).
4. How are convection currents
related to plate boundaries?

The rising part of a convection current
spreads out as it reaches the upper
mantle and causes divergent boundaries
to form.

The downward part of a convection
current occurs where a sinking force pulls
plates together, creating a convergent
boundary.
5. List the questions about mantle
convection that remain unanswered
Are mantle convection currents
permanent?
 Do they shift positions over time?
 How does a convection current start?
 What causes one to stop?
 Does convection only take place in the
upper mantle, or does it also take place in
the core?
