Unit 8: The Earth's internal energy

UNIT 8: THE EARTH’S INTERNAL ENERGY

THE EARTH IS A SOURCE OF HEAT

Our planet has got an internal energy called geothermical energy.

This internal heat comes from Celestial bodies impacts. Radioactives elements like uranium.

This internal energy causes: Movement of continents. Volcanoes Earthquakes Mountain ranges and ridges. Igneous and metamorphic rocks.

DO THE CONTINENTS MOVE?

There was a supercontinent called Pangaea which split up into different fragments giving the continents and oceans that nowdays we know.

This theory was given by Alfred Wegener in 1912 and it is known as continental drift.

Continental drift theory was based on some evidences: Geographic evidences: The continents fit

together perfectly at the edge of their continetal shelves. (South America and Africa)

Climatic evidences: There is glacial till deposits in the southern hemisphere (Brasil or Congo)

Biological evidences: Living animals in widely separated lands are similar.

Paleontological evidences: Similar plant and animal fossils are found around different continent shores.

In 1960, later discoveries completed the continental drift theory, and now it is called tectonic plates theory.

STRUCTURE OF THE EARTHContinental crust

Oceanic crust

Litosphere

The solid part of the Earth is called litosphere, and it is split up in big fragments or plates, like a puzzle. They are floating over a mantle’s layer called astenosphere.

Types of tectonic plates : Oceanic plate: It is formed by oceanic

litosphere. Continental plate: It is formed by

continental litosphere. Mixed plate: It is formed by continental and

oceanic litosphere. These plates lie above the magma and are

moved by the convection currents of the mantle.

The distribution of major earthquakes and volcanoes mostly coincide with today’s plate boundaries.

Convergent boundaries:areas where the litospheric plates are pushed together. Ex:Atlantic ocean.

Divergent boundaries: areas where the litospheric plates are moving away.Ex:Himalaya

Transform boundaries: areas where the litospheric plates are sliding laterally. Ex: San Andreas Fault.

ACTIVITIES1. List four things which prove that there is

internal energy in the Earth.2. Define the following terms in simple words:

a. Continental drift.b. Tectonic plate.

3. What led Wegener to think that Africa and South America had been joined together in the past? Are there more evidences?

4. Why do we say that the litospheric plates are like the pieces of puzzle?

5. Look at the map on page 152. Look at the arrows which show the displacement of the plates. Name two continents which are moving apart and two continents which are colliding.

6. Explain what a divergent boundary is and give an example.

7. Explain what a convergent boundary is and give an example.

8. Explain what a transform boundary is and give an example.

9.Define the following terms:a. Hypocentre.b.Earthquakec.Epicentre

10. Draw an earthquake and label the elements in English and Spanish.

11.Draw a volcano and label the elements in English and Spanish.

WHAT IS A VOLCANO?

It is an opening in the Earth's crust through which molten lava, ash, and gases are ejected.

These molten rock materials are known as magma within the crust, and lava outside the crust.

Products expelled during a volcano eruption:Liquid materials: Lava.Gases: Water vapor, Hydrogen sulfide (H2S),

Carbon dioxide(CO2).Pyroclastics: Ashes, lapillis, volcanic bombs.

TYPES OF VOLCANOES

Hawaiian volcano: The calmest eruption. A very fluid lava. Example: Kilauea.

Strombolian volcano: The magma is more viscous and the eruption is mildly explosive. Example: Stromboli.

Pelean volcano: The most viscous magma. Massive explosive eruptions with hot volcanic ash. Very destructive. Example: Mont Pelée.

ATTENUATED VULCANISM

Fumaroles: A hole in a volcanic area from which hot smoke and gases escape.

Thermal springs: a natural spring of warm mineral water.

Geysers: A spring that discharges steam and hot water.

A sudden movement of the earth's crust caused by the release of stress accumulated along geologic faults or by volcanic activity.

Elements of an earthquake: Hypocenter or focus: It is the place inside the

Earth where an earthquake originates. Epicenter: It is the point on the Earth's

surface that is directly above the hypocenter. Seismic waves: Are waves that travel through

the Earth. Can pass through the earth like water.

EARTHQUAKES