Science - Term 1

Topics covered: Formation of the Earth, Continental drift

Why is the inner core solid?

The inner core is solid owing to the extreme pressure

How thick is the inner core?

About 1200km thick

Around what temperature is the inner core?

The inner core’s temperature reaches up to 7000 degrees celsius

What is the effect of the inner core having 3.5million times of atmospheric pressure?

It pushes atoms very close together, making it harder for them to move freely, raising the melting point of metals

What is the outer core primarily composed of?

Molten iron and nickel

What does the temperature range between in the outer core?

Temperatures are mostly between 4000 degrees celsius and 6000 degrees celsius

About how thick is the outer core?

The outer core is about 2300km thick

The three magnetic metals in the Earth are…

Iron, Nickel, Cobalt

What does the temperature range in the mantle?

The temperature ranges mostly ranges between 500 and 2000 degrees celsius

About how thick is the mantle?

The mantle is about 2900km thick

What does the crust include?

The crust includes landforms, rocks and soil, it is mostly solid rock and has high strength

How thick is the crust and how does it vary?

It varies in thickness from as little as 5km under the ocean to about 70 km under mountain ranges (an example includes the HImalayas)

Define continental drift

Continental drift is the gradual movement of the continents across the surface of the Earth

List the five main points of the continental drift theory

1. Continents fit like a jigsaw puzzle

2. Fossils of the same plant/species found on opposite sides of the ocean

3. Matching rock formations on opposite sides of the ocean

4. Coal discovered above the arctic circle

5. Evidence of ancient glaciers in locations now too warm to produce glaciers (glacial striations)

Where was Wegener wrong

1. Wegener thought that the continents may have ploughed through the ocean crust like ice breakers smashing through ice

2. Wegener’s estimate of the velocity of continental drift motion, 2.5 meters per year was incredibly high

Wegener’s theory is now replaced by which theory to correct his misconceptions

The plate tectonic theory

List the whole theory of continental drift - By Alfred Wegener (Both incorrect and correct terms)

• Earth’s continents are moving

• No explanation for why the continents are moving

• Earth’s continents were once joined

• Wegener thought that the continents smashed through the crust like an ice breaker

• Wegener though that the continents moved at a speed of 2.5 meters per year

How was the solar system formed?

The solar system was formed about 4.5 billion years ago from a dense cloud of interstellar gas and dust

Explain the sun’s birth

Gravity pulled material in, and hydrogen atoms began to combine forming helium

Define Pangea

A massive supercontinent that joined nearly all of Earth’s landmasses into one giant supercontinent

What is Panthalassa?

The vast sea that surrounded Pangea

The crust and the upper mantle together make up the structure known as the…

Lithosphere

What does the theory of plate tectonics suggest about the structure of the lithosphere

That it is divided up into a number of ‘plates’

List the seven major plates

• African

• Antarctic 

• Eurasian 

• Indo - Australian

• North American 

• South American 

• Pacific

All the plates float on which layer? And how thick is this layer typically?

All the plates float on the asthenosphere which is typically 200km thick

Explain what makes the plates move in this layer

Convection currents in the mantle keep the magma moving, the movement of magma moves the plates

Define convection currents

Convection currents are heat driven circulation patterns in fluids (liquids and gases), where warmer, less dense material rises and cooler denser material sinks

Hot substances …

Expand

Cold substances …

Contract

Molten rock below the surface of the Earth is called

magma

Once magma is on the Earth’s surface it is known as

lava

Divergence:

When the plates move away from each other

Convergence:

When the plates move towards each other and collide

Translation:

Plates slide past each other

What happens at a divergent boundary?

Earthquakes

Volcanic activity

Sea floors spreading

Rift valleys

Mid ocean ridges

What happens at a convergent boundary?

Earthquakes

Volcanic activity

Mountain building

Subduction

What happens at a transform boundary?

Earthquakes

What is folding?

Folding is when forces underneath the Earth cause rocks to bend without breaking

Folds that bend upwards are called

Anticlines

Folds that bend downwards are called

Synclines

What is a fault?

A fault is a fracture in rock where there has been displacement of rock

What is it called when movement along a fault is sideways

It is called a transform fault

When rocks have been forced upwards it is called…

When rocks have been forced upwards it is called a reverse fault

Reverse faults appear on rocks that have been

Squeezed together

When the rocks on one side slip downwards it is called a…

Normal fault

Normal faults appear in rocks that have been

Stretched and pulled apart

How do Earthquakes occur?

Earthquakes occur when jammed plates suddenly slip past each other

How do earthquakes away from boundaries happen

• Movement of hot material in the mantle being felt at the surface

• Movement along a fault that is buried deep into the ground

• Movement along partial fractures in existing places

What is the focus

The focus is the name for the location in the Earth’s crust where an Earthquake originates

The energy released by earthquakes are

seismic waves

What is the epicentre?

The epicentre of an earthquake is the point directly above the focus

What is a wave

A wave is th etransfer of energy without the transfer of matter

What are the three types of waves generated by earthquakes

P - waves

S - waves

L - waves

What are P - waves?

P - waves are compression waves also known as primary waves

Which wave is the fastest?

P - waves

Where can the P - wave travel

The p - wave can travel to the inner core, the outer core and the mantle

Which waves are after the P - waves?

The s waves

What are the s-waves

The secondary waves

Why are the s and p waves called body waves

Because they are able to travel through the interior of the Earth

What are L - waves

L - waves are surface and travel around the Earth’s surface

Even though L-waves move much more slowly what are they responsible for

The majority of the Earthquake’s power

Describe what happens when a plate carrying oceanic crust collides with a plate carrying continental crust

The more dense oceanic crust will subduct

Describe what happens when two plates carrying oceanic crust collide

When two plates carrying oceanic crust collide the denser plate subducts usually the older plates

Describe what happens when two plates carrying continental crust collide

When two plates carrying continental crust collide, the crust is forced upwards

What was the early assumption made my scientists to explain the motion of the continents

The early assupmtion made by scientists