Science - Plate Tectonics

Question 1

Alfred (Wegner) Wagwan G’s 2 pieces of evidence for Continental Drift

Answer 1

• The continents fit together like a jigsaw.
• There are fossils of the same species on diferent continents.

Question 2

Harry Hess’ 3 pieces of evidence for Seafloor Spreading

Answer 2

• Magnetic striping
• The seafloor further from the ridges is older than the rock closer to the ridges
• There is less sediment ontop of the crust that is close to the ridges compared to the crust that is far from the ridges

Question 3

Magnetic Striping

Answer 3

When the magnetite in the magma aligns with the earth’s magnetic field which changes every few hundred thousand years, causing the magnetite to point in an opposite direction. This creates stripes of rock with the magnetite pointed one way, and stripes of rock with the magnetite pointed the other way.

Question 4

What is a Diverging Boundary?

Answer 4

Where the plates move away from each other, creating new crust.

Question 5

What is a Converging Boundary?

Answer 5

When the plates move towards each other, destroying crust.

Question 6

What is a Transform Boundary?

Answer 6

When the plates move past each other.

Question 7

Subduction

Answer 7

When a plate goes underneath another plate in a converging bourndary.

Question 8

Characteristics of oceanic crust

Answer 8

• Denser
• Thinner
• Contains heavier elements (Fe, Mg, etc.)
• It is wet and slippery as well as containing lots of sealife due to being underwater

Question 9

Characteristics of continental crust

Answer 9

• Less dense
• Thicker
• Contains lighter elements (Al, Si, etc.)
• It is dry and desert like, containing humans, civiliazations as well as mostly of the known animal species.

Question 10

Theories for plate movement

Answer 10

• Convection currents
• Gravity

Question 11

Convection currents

Answer 11

When the hot magma rises from the asthenosphere, hitting the plates and drags them before sinking back down

Question 12

How does gravity make plates move?

Answer 12

Either:
1. Slab pull, where gravity pushes on the crust near the subduction zone
or:
2. Ridge push, where the new crust that formed at the ridge pushes older crust down.

Question 13

Seafloor spreading

Answer 13

A theory where new rock is formed at mid-ocean ridges and slowly moves outwards.

Question 14

Tectonic plates

Answer 14

Massive slabs of rock that make up the earths crust.

Question 15

Lithosphere

Answer 15

The highest layer of earth made of the crust and upper mantle. This layer is rigid.

Question 16

Asthenosphere

Answer 16

The second layer of earth made of lower mantle. This layer is flexible.

Question 17

The outer core of the earth

Answer 17

The second deepest layer of the earth made of liquid metal

Question 17

Rifting

Answer 17

A process to split a continent into two where a continent would crack and fill with water from the oceans, folowed by seafloor spreading.

Question 18

Landform made by continental-continental converging boundaries

Answer 18

Mountain ranges

Question 19

Landform made by oceanic-continental converging boundaries

Answer 19

Mountains, volcanoes and trenches

Question 20

Landform made by oceanic-oceanic converging boundaries

Answer 20

Island Arcs, Volcanoes

Question 21

Landforms made by transfom boundaries

Answer 21

Mountains, Fault lines

Question 22

Landforms made by divergent boundaries

Answer 22

Rift valleys, Ocean ridges and Volcanoes

Question 23

What are 4 things that volcanoes release when erupting?

Answer 23

• Ash
• Lava
• Gas (Steam & Hydrogen sulfate)
• Scoria (Solid volcanic rock)

Question 24

Why did the scientific community initially reject Wegener’s theory?

Answer 24

He couldn’t explain how the continents moved

Question 25

Magma vs Lava

Answer 25

Magma is undergorund while Lava is aboveground

Question 26

Hot spot volcanoes

Answer 26

Isolated weak spots within a plate where a lot of magma is present. When the magma floats to the surface it creates a hot spot volcano.

Question 26

How do earthquakes occur?

Answer 26

When tectonic plates that are held together with friction eventually slip, releasing energy into the surrounding rock or water.

Question 27

How are earthquakes measured?

Answer 27

Using a seismometer

Question 28

Primary waves

Answer 28

Waves from an earthquake that move back and forth. They travel the fastest out of the three waves.

Question 29

Secondary waves

Answer 29

Waves from an earthquake that move up and down. They travel at speeds between Primary and Surface waves

Question 30

Surface waves

Answer 30

Waves from an earthquake that travel in a rolling motion. They travel the slowest and are the most destructive.

Question 31

Where do earthquakes occur

Answer 31

Most commonly on plate boundaries, especially on transform boundaries.

Question 32

Focus

Answer 32

Where the slip occurs in an earthquake

Question 33

Epicentre

Answer 33

The point on the suface above the Focus

Question 34

When does a tsunami occur?

Answer 34

When an earthquake occurs in the ocean

Question 34

Ritcher scale

Answer 34

A logarithmic scale for earthquake severity

Question 34

Magma moves through ____ in the earths crust

Answer 34

Weaknesses