1. Causes of Plate Motions
Chapter 17, Section 4

2. 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.

3. 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….

4. 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).

5. 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.

6. 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?

7. First Nation’s Perspective of Plate tectonics
First Nations Peoples accounts of events are passed though oral story telling traditions
This means that stories have been passed by many generations including the earthquake of the 1700s.

8. First Nation’s Perspective of Plate tectonics
The exact use of the term tectonic plates may not be present, but understanding that the Earth shakes shows an inherent understanding that the Earth is in motion.
An earthquake in 2012 near Haida Gwaii has been memorialized in a legacy pole