2. CHAPTER 1 LIVING WITH
TECTONIC HAZARDS
Gateway 1: Why are some area more prone to
tectonic hazards?
a. What is a natural hazard?
b. What is the internal structure
of the Earth?
3. • A natural hazard is a natural event that threatens
human lives and causes damage to property.
a. What is a natural hazard?
4. Examples of natural hazards
• Tectonic
hazards
• Earthquakes
• Volcanic eruptions
• Tsunamis
• Climate-
related
hazards
• Droughts
• Floods
• Storms
a. What is a natural hazard?
6. b. What is the internal structure of the earth?
7. • Makes up the Earth’s rigid outer shell
• When the rocks in the lithosphere melt,
hot molten rock called magma is formed.
Lithosphere
= Crust + Uppermost mantle
b. What is the internal structure of the earth?
8. • A tectonic plate is made up of the lithosphere
(i.e. crust + uppermost mantle).
• The earth’s crust is broken into several pieces
of tectonic plates.
• These plates move in relation to one another.
• Tectonic plates can be made up of:
– oceanic crust
– continental crust or
– a combination of both
c. What is a tectonic plate?
9. Oceanic crust vs Continental crust
Oceanic Crust
• Located beneath deep
ocean
• Very thin — between 5
and 8 km
• Denser (e.g. basalt)
Continental Crust
• Located beneath land
masses and under
shallow seas
• Very thick — between 30
and 60 km
• Less dense (e.g. granite)
c. What is a tectonic plate?
10. 1. Convection currents
•Convection currents are movements of heat within the
mantle.
•Material in the mantle is heated by the core.
•This causes convection currents in the molten mantle
material.
•Mantle expands, rises and spreads out beneath the
plates.
•Plates are dragged along and move away from each
other.
d. Why do tectonic plates move?
11. 1. Convection currents
•Subsequently, the hot molten mantle cools slightly
and sinks, pulling the plates along
•Hence plates move towards each other.
•The sinking mantle material heats up again as it
nears the core and the whole process repeats.
d. Why do tectonic plates move?
12. Tectonic plates float on molten mantle, driven by heat
energy/convection currents
Plates moving away from each other
Platesmoving
towardseachother
Plates
moving
towards
eachother
Plates
Ocean floor
d. Why do tectonic plates move?
13. 2. Slab-pull force
• This occurs when an oceanic plate (denser) subducts
under a less dense plate and pulls the rest of the
plate along.
• The subducting plate drives the downward-moving
portion of convection currents.
• While mantle material away from the subduction
zone drives the rising portion of convection currents.
d. Why do tectonic plates move?
14. Changing positions of the earth’s continents
• Plate movements have altered the distribution of
the earth’s land masses over several hundred
million years.
d. Why do tectonic plates move?
Editor's Notes
Suggested activity:
Ask students to read the article on http://www.channelnewsasia.com/stories/singaporelocalnews/view/337625/1/.html.
Prompt them to explain if the incident is a natural hazard.
Suggested activity
Recap the internal structure of the earth with students with the website: http://www.learner.org/interactives/dynamicearth/structure.html
Suggested activity:
Demonstrate convection currents with the video: http://www.youtube.com/watch?v=PdWYBAOqHrk&feature=fvwrel
Suggested activity:
Let students watch a video on the changing positions of the earth’s continents: http://www.youtube.com/watch?v=WaUk94AdXPA
