Plate techtonics, evidence & how it works

Question 1

What did Albert Wegener discover in 1910 and what did he call this?

Answer 1

In 1910 Alfred Wegener realised that the surface of the world had moved in the past.

He realised that the continents had moved and he called this “Continental Drift”.

Question 2

What is the evidence for continental drift?

Answer 2

1. Jigsaw of continents
2. Geological
3. Fossil Record
4. Climatic

Question 3

What is the Jigsaw Puzzle FitOff The Continents?

Answer 3

Wegner noticed that the coastlines of South America and Africa fit like the pieces of a puzzle. This was not a coincidence because it indicates that the two continents were once united and had since then drifted apart.

Question 4

What is the fossil record evidence for continental drift?

Answer 4

Similar species of fossils were recognized between the east coast of South America and the west coast of Africa.

(For example, the fern Glossopteris which grew in a sub-polar climate was found in the rocks of Africa, Australia, India, and South America. This indicated that the landmasses were once a part of Gondwanaland).

Question 5

What is the geological evidence for continental drift?

Answer 5

Wegener found rocks of the same type and age on both sides of the Atlantic Ocean. He thought that the rocks formed side by side. These rocks then drifted apart on separate continents.

Wegener also matched up mountain ranges across the Atlantic Ocean. The Appalachian Mountains were just like mountain ranges in eastern Greenland, Ireland, Great Britain, and Norway. Wegener concluded that they formed as a single mountain range. This mountain range broke apart as the continents split up. The mountain range separated as the continents drifted.

Question 6

What is the climatic evidence for continental drift?

Answer 6

Coral reefs are found only in warm water. Coal swamps are also found in tropical and subtropical environments.

Wegener discovered ancient coal seams and coral reef fossils in areas that are much too cold today. Wegener thought that the continents have moved since the time of Pangaea.

Question 7

What is Palaeomagnetism?

Answer 7

Palaeomagnetism is the study of the record of the Earth’s magnetic field in rocks, sediment, or archaeological materials.

Question 8

What do certain minerals in rocks lock-in?

Answer 8

Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form.

Question 9

What information does this lock-in record provide?

Answer 9

This record provides information on the past behaviour of Earth’s magnetic field and the past location of tectonic plates.

Question 10

Continents have moved over time but how or why could they move? How does it work?

Answer 10

The Earth is a giant ball of molten material floating in space.

The Earth hasn’t cooled down from when it was formed 4.6 billion years ago.

The inside of the Earth is very, very hot. It is estimated that the temperature at the centre is 4,500c (as hot as the surface of the Sun!)

Only the outer layer is cool enough to be a solid- this is the crust.

Question 11

What is the outer layer of the Earth called?

Answer 11

the crust

Question 12

When was the Earth formed?

Answer 12

4.5 billion years ago

Question 13

What is the structure of the Earth (6 terms)?

Answer 13

• ALMMOI-

Asthenosphere:

Lithosphere:

Mesosphere:

Mantle:

Outer Core:

Inner Core:

Question 14

What is the Asthenosphere?

Answer 14

The upper part of the Earth’s mantle, extending from a depth of about 75 km (46.5 mi) to about 200 km (124 mi).

The asthenosphere lies beneath the lithosphere and consists of partially molten rock.

Question 15

What is the Lithosphere?

Answer 15

The lithosphere is the solid, outer part of the Earth.

The lithosphere includes the brittle upper portion of the mantle and the crust, the outermost layers of Earth’s structure. I

It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below

Question 16

What is the Mesosphere?

Answer 16

In geology, the mesosphere refers to the mantle in the region under the lithosphere and the asthenosphere, but above the outer core.

Question 17

What is the mantle?

Answer 17

The mantle is the mostly-solid bulk of Earth’s interior.

The mantle lies between Earth’s dense, super-heated core and its thin outer layer, the crust.

The mantle is about 2,900 kms (1,802 miles) thick, and makes up a whopping 84% of Earth’s total volume.

Question 18

What is the Outer Core?

Answer 18

The outer core of the Earth is a fluid layer about 2,300 km (1,400 mi) thick and composed of mostly iron and nickel that lies above Earth’s solid inner core and below its mantle. Its outer boundary lies 2,890 km (1,800 mi) beneath Earth’s surface.

Question 19

What is the Inner Core?

Answer 19

The Earth’s inner core is the Earth’s innermost part and according to seismological studies, it has been believed to be primarily a solid ball with a radius of about 1,220 kms (760 miles), which is about 70% of the Moon’s radius.

It is composed of an iron–nickel alloy and some light elements.

Question 20

What is the crust made of?

Answer 20

The crust is not one solid piece. It appears solid but is elastic- it can be warped and stretched.

It is very thin and is made up of several large pieces that float on the mantle.

The crust fits together like a giant jigsaw.

These pieces move about the surface of the Earth.

They are called Plates. This movement is called Plate Tectonics.

However, the movement is not fast but in a few cms each year. In an average persons lifetime we would notice a movement of only a few feet. But over millions of years the plates will move hundreds of miles.

Question 21

How many types of crusts are there?

Answer 21

There are two types of crust:

Oceanic- new (formed within the last 200 million years), thin (between 10km and 30km) & heavy- sinks into the mantle.

Continental- old (formed up to 2 billion years ago), thick (between 50km and 100km thick) & light- floats easily onto the mantle.

The type of crust is important in how the plates behave when they move.

Question 22

In which direction do the plates move?

Answer 22

Some plates move into each other.
Some plates move away from each other.
Some plates move alongside each other.
When they move they create volcanoes, earthquakes, mountains, ocean trenches & tsunamis

See notes for images

Question 23

How do the plates move?

Answer 23

The plate move due to currents in the mantle beneath the crust.

The mantle next to the outer core is heated and rises due to convection.

The hot mantle in the current rises towards the crust.

The crust stops the hot mantle and it has no choice but to travel or flow beneath the crust.

As the hot mantle then flows under the crust it makes the crust move in the same direction as the current.

see notes for image

Question 24

Where do volcanoes happen?

Answer 24

Volcanoes happen when plates move apart and into each other.

Question 25

Where do earthquakes happen?

Answer 25

Earthquakes happen at all plate boundaries.