UNIT 7. THE EARTH’S DYNAMICS

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

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?

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.

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

formedEx: 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

MID-ATLANTIC RIDGE

PLATE TECTONICS THEORY Plate boundary interaction produces

geological processes: Volcanoes Earthquakes Mountain ranges And others

ACTIVITIES1. Choose the correct answer:A) Along convergent boundaries there usually are: 1) Trenches 2) Ridges 3) PlateausB) In divergent borders lithosphere is: 1) destroyed 2) created 3) Neither created nor destroyedC) 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?

3. Convergent or divergent boundaries?a)The formation of mountain rangesb) The widening of an oceanc) The contraction of an oceand) The formation of ocean ridges4. 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.

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.

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.

EUROPEAN RISK MAP

ACTIVITIES5. 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 rocksc) Seismic waves 3. Point where rocks move or breakd) Focus or hypocentre 4. Movement of the land caused by plate dynamics

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.

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.

ACTIVITIES7. 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.

9. Match:a) Pyroclasts 1. Earthquakesb) Epicentre 2. Volcanoesc) Hypocentred) Lavae) Crater