Unit 7. 2º ESO. Earth's dynamics.

1. UNIT 7. THE EARTH’S
DYNAMICS

2. UNIT OBJECTIVES
 To learn about plate tectonics.
 To understand earthquakes and their risks.
 To understand volcanoes and their risks.

3. STOP AND THINK
 Why do you think lithospheric plates move?
 What is a volcano? And an earthquake?
 How do you think the mountain ranges were formed?

4. PLATE TECTONIC DYNAMICS
 The internal energy of the Earth causes
convection currents in the mantle.
 This movement breaks and changes the size of
tectonic plates.

5. PLATE
BOUNDARIES
CONVERGENT
BOUNDARIES
DIVERGENT
BOUNDARIES
TRANSFORM
FAULT
BOUNDARIES- They move
towards each
other.
- One of them sinks
inside the mantle
(SUBDUCTION)
- The lithosphere
is destroyed.
- Trenches are
formed
Ex: Mariana trench
- They move away
from each other.
- Molten rocks rise and
new lithosphere is
created.
-Oceanic ridges are
formed.
-Ex: Atlantic ridge
- They move
laterally in
opposite
directions.
- Lithosphere is not
created or destroyed.
Ex: San Andreas
fault

6. MID-ATLANTIC
RIDGE

8. PLATE TECTONICS THEORY
 Plate boundary interaction produces geological
processes:
 Volcanoes
 Earthquakes
 Mountain ranges
 And others

9. ACTIVITIES
1. Choose the correct answer:
A) Along convergent boundaries there usually are:
1) Trenches 2) Ridges 3) Plateaus
B) In divergent borders lithosphere is:
1) destroyed 2) created 3) Neither created nor destroyed
C) In transform fault boundaries, the plates move:
1) In the same direction 2) Against each other
3) In opposite directions
2. The African plate has a divergent boundary called
Rift Valley , which is breaking into two pieces little by
Little. What do you think will happen as time goes by?

10. 3. Convergent or divergent boundaries?
a)The formation of mountain ranges
b) The widening of an ocean
c) The contraction of an ocean
d) The formation of ocean ridges
4. True or false? Correct them.
a) When the movements of the Earth’s mantle touch
the lithosphere, they make the plates break or move.
b) In divergent boundaries the plates move towards
each other.
c) Lithospheric plates are dynamic.
d) The interactioon between the borders of the plates
are the cause of earthqueakes and volcanoes.
e) The movement of plates is very quick.

11. WHAT IS AN
EARTHQUAKE
 It’s a movement of the land
caused by the forces from the
lithospheric dynamics.
 HOW IT OCCURS?
1. Tectonic forces compress and
stretch the rocks.
2. The tensión accumulates.
3. The rocks can’t bear the
tension and they move or
break.
4. The seismic waves reach the
surface.

12. SEISMIC RISK
 It’s the probability of a human or economic
disaster occuring in an area due to earthquakes.
 Populated areas near the plate boundaries have a
great seismic risk.
 Risk maps show the areas where the most
earthquakes occur.

13. EUROPEAN RISK MAP

15. ACTIVITIES
5. Look at the risk map of Europe and indicate what
countries have the highest risk. And in Spain? Do you live
in an area with some risk?
6. Match:
a) Earthquake 1. Point on the Surface above the epicentre.
b) Epicentre 2. Vibrations which extend through rocks
c) Seismic waves 3. Point where rocks move or break
d) Focus or hypocentre 4. Movement of the land caused by
plate dynamics

16. VOLCANOES AND THEIR RISKS
 It’s an opening on the surface of the Earth where
gases, liquids and solids from the lithosphere are
released.
Magmatic chamber: This is
the area in the lithosphere
where magma accumulates.
Pipe: This is the passage
that connects the magma
chamber to the opening on
the surface.
Volcanic cone: This is the
cone-shaped build-up of
volcanic materials expelled by
the volcano.Crater: This is the opening
of the volcano.
Pyroclasts and gases:
Fragments of rocks and
gases are expelled.

17. VOLCANIC RISK
 It’s the probability of a
human or economic disaster
occuring in an area due to
volcanic activity.
 The most dangerous
volcanoes expel clouds of
toxic gases and bruning
pyroclasts.
 To prevent:
 Risk maps
 Build dykes and shelters.

18. ACTIVITIES
7. Fill in the blanks:
a) The________ _________ is the area where magma
accumulates.
b) The_______ is the passage which connects the_____
______ to the opening surface.
c) The _______ is the opening of the volcano.
d) The______ ______ is a structure similar to a
mountain.
8. True or false? Correct them.
a) The liquid materials of a volcano are called pyroclasts.
b) The solid materials of a volcano are called lava.
c) The Canary Islands, Campo de calatrava and Cape
Gata are Spanish volcanic areas.

19. 9. Match:
a) Pyroclasts 1. Earthquakes
b) Epicentre 2. Volcanoes
c) Hypocentre
d) Lava
e) Crater