dynamic planet earth

Question 1

rock cycle

Answer 1

1. Magma cools to form igneous rocks
2. Sediment is compacted and cemented into sedimentary rocks
3. Both sedimentary and igneous rocks can be changed under heat and pressure into metamorphic rocks.
4. All rocks can remelt and turn back into magma

Question 2

atmosphere

Answer 2

The atmosphere is the air on Earth. It covers the planet in a thin layer and the ozone layer protect the Earth’s surface from UV radiation.

Question 3

biosphere

Answer 3

The biosphere is the life support system of our planet. The biosphere includes all the ecosystems on Earth. Cycles of carbon and nitrogen are important for life on Earth.

Question 4

lithosphere

Answer 4

The lithosphere includes all the rocks in the crust and the rock cycle shows how rocks change through the lithosphere.

Question 5

mantle

Answer 5

the semi-liquid, very high temperature layer below the crust. The cooler sections near to the crust is less mobile than the hotter section next to the core.

Question 6

core

Answer 6

the layer at the centre of the Earth. This layer is divided into 2 sections: the liquid outer core, and the solid inner core.

Question 7

Archaeozoic and Proterozois

Answer 7

after the first billion years, bacteria developed. Slowly, the atmosphere started to rise in oxygen.

Question 8

Mesozoic

Answer 8

Age of dinosaurs, early mammals, and flowering plants develop.

Question 9

Cainozoic

Answer 9

age of mammals, grasses, and humans develop.

Question 10

radiometric time scale

Answer 10

Radioactive isotopes decay at a known half-life. Uranium-235 has a half-life of 704 million years and it decays to form an isotope of lead. By comparing the amounts of Pb-207 and U-235 a rock sample has in it, the age of the rock can be estimated.

Question 11

zircon dating

Answer 11

One of the most widely used systems looks at the decay of uranium isotopes in zircon, which is a mineral common to many rocks.

Question 12

magnetic striping on ocean floor

Answer 12

rocks further away from the midlines of mid-ocean ridges are older than those that are closer to the midlines. The age of the rocks can be confirmed by using radioisotope dating techniques and paleomagnetism

Question 13

index fossils

Answer 13

these are well-known fossils that can be used as indicators of a rock’s age. This is because these fossils have been studied and dated by other scientists.

Question 14

geological strata

Answer 14

Geological strata are layers of rocks (sedimentary, soil, or igneous) that formed at the Earth’s surface.

Each layer has characteristics in it that separate it from other laters.

Characteristics can include:
Different fossils, including index fossils
Evidence of a geological activity (volcano, tsunami, earthquake)
Evidence of weather and climate (Antarctica ice cores, bushfires)

Question 15

wegner’s theory of continental drift

Answer 15

a hypothesis that all continents were once connected in a single landmass called Pangaea that broke apart and have been slowly drifting away from about 200 million years

Question 16

folding

Answer 16

can turn rock sequences vertically or upside down.

Question 17

faulting

Answer 17

can push older rocks over younger ones.

Question 18

volcanic activity

Answer 18

Igneous rock can be created from magma pushing through surrounding rocks from below. They will therefore be younger than the rocks immediately above and below them.

Question 19

convection process

Answer 19

Heat gives particles more kinetic energy. They spread out further, so the material is less dense.
Less dense material rises. It pushes material on top of it aside.
As the material moves away from the heat source, it cools. Particles have less kinetic energy and so are more attracted towards each other. The material becomes more dense and sinks.

Question 20

convection

Answer 20

The transfer of heat by the movement of a fluid

Question 21

Movement of Plates and Mantle Convection Currents

Answer 21

1. Heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core.
2. The convection currents move the plates.
3. Where convection currents diverge near the Earth’s crust, plates move apart.
4. Where convection currents converge, plates move towards each other.

Question 22

Subduction and Gravity

Answer 22

A subduction zone is a convergent plate boundary where a more dense plate sinks below a less dense plate.

1. Oceanic plate is more dense than the continental plate, so gravity makes it sink underneath the continental plate.
2. As the oceanic plate sinks, friction and heat melt the crust and evaporate liquid in the crust (eg. water) to gases.
3. Gases (eg. steam) rise through the continental plate, often forming volcanoes

Question 23

Seafloor Spreading

Answer 23

• As subduction makes one side of the oceanic plate sink due to gravity, the other side of the oceanic plate is being pulled away from another plate.
• This is an example of a divergent plate boundary.
• As the crust here is thin and weakened, the less dense magma underneath rises to the surface due to convection.
• The magma is cooled by the ocean water and forms igneous rock, often basalt.
• This new rock is more dense than rocks found on continental plates, which is why oceanic plates are denser than continental plates.

Question 24

convergent boundary

Answer 24

• Subduction zones are convergent boundaries between oceanic crust and continental crust.
• Convergent boundaries can also occur between continental crusts.
• Forms mountains eg. Himalayas, and volcanoes eg. Ring of Fire

Question 25

divergent boundary

Answer 25

• A divergent boundary occurs when two tectonic plates move away from each other.
• Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create new oceanic crust.
• In the ocean, ridges form at divergent boundaries eg. Mid-Atlantic Ridge
• On land, rift valleys form eg. Rio Grande

Question 26

transform boundary

Answer 26

• Two plates sliding past each other forms a transform plate boundary.
• Structures that cross a transform boundary are split into pieces and carried in opposite directions, creating a fault valley (eg. San Andreas fault) or undersea canyon.
• Earthquakes are common along these faults.
• In contrast to convergent and divergent boundaries, crust is cracked and broken at transform margins, but is not created or destroyed.

Question 27

folding

Answer 27

• Folding is the process where layers of rock bend and crumple without breaking.
• Folding can occur far from plate boundaries as well as near the edges of colliding plates.
• Folds that bend upwards are called anticlines. Those that bend downwards are called synclines.
• Generally folding occurs below the surface of the Earth and is not visible unless exposed by weathering and erosion. Folding can often be seen in road cuttings or in cliffs.

Question 28

faulting

Answer 28

• Faulting is the movement of rock layers along a crack.
• Faults (cracks) can occur at plate boundaries or away from them.
• Example: The Gulf region of South Australia has been formed by a series of faults. Two blocks of crust have dropped down between faults to form Spencer Gulf and Gulf St Vincent.

Question 29

Folding and the Movement of Tectonic Plates and the Formation of Mountain Ranges

Answer 29

• Fold mountains are created where two or more tectonic plates are pushed together at convergent boundaries, usually between colliding continental crust.
• Rocks on the edge of plates are often weaker than in the continental interior, so they are more easily folded. This makes fold mountains more common on the edges of plates.
• Fold mountains are the most common type of mountain in the world. Examples of fold mountains include the Himalayas, Andes, and Alps.

Question 30

convergent boundary volcanoes

Answer 30

Where ocean plates converge with continental plates the ocean sediments are pushed under the continental plate. The ocean sediments are melted as they are pushed down into the mantle and become magma. The molten lava wells up to erupt from a volcano which causes it to push upwards through the continental crustal plate. If there is sufficient magma and pressure it will reach the surface as lava resulting in a volcano.

Question 31

divergent boundary volcanoes

Answer 31

At divergent plate boundaries, the tectonic plates are moving away from one another. The Earth’s crust is pulled apart to create a new pathway for rising hot magma to flow on to the surface. Volcanoes can sometimes form in these settings.

Question 32

locations

Answer 32

Volcanoes are most common along convergent plate boundaries between oceanic and continental crust. An example is the Ring of Fire, an area in which the majority of earthquakes and volcanoes happen. This is because these areas are situated on convergent plate boundaries.

Question 33

active, dormant, extinct volcanoes

Answer 33

• An active volcano is a volcano that has had at least one eruption during the past 10,000 years.
• A dormant volcano is an active volcano that is not erupting, but supposed to erupt again.
• An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future.

Question 34

earthquake

Answer 34

An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth’s crust and cause the vibrations that we feel. These waves originate from the focus. The point on the surface above the focus is the epicentre. Most earthquakes occur at tectonic plate boundaries, but some can occur away from plate boundaries, along faults.

Question 35

seismic waves

Answer 35

Seismic waves, like all types of waves, transfer energy without transferring matter. A seismic wave travels across the world, but doesn’t move the ground across the world. It makes the ground vibrate on the spot.

Question 36

P-waves

Answer 36

Longitudinal – makes objects vibrate along the direction of travel. The waves travel left to right, as do the particles. This type of seismic wave travels the fastest. It can travel through solids, liquids and gases.

Question 37

s-waves

Answer 37

Transverse – makes objects vibrate perpendicular to the direction of travel. The waves travel left to right, whereas the particles vibrate up and down. S-waves are slower than P-waves. Only travels through the crust and mantle of the Earth.

Question 38

tsunami

Answer 38

Series of ocean waves caused by undersea earthquakes

Question 39

how a tsunami occurs

Answer 39

• All waves are started by vibrations. The earthquake pushes the water above it, causing a water wave
• In deep water, this wave travels fast, but its wavelength is long
• As the wave enters shallow water, it changes medium, and slows. However, the wavelength also shortens and the amplitude increases. The extra water that increases the height of the wave comes from water being sucked back from the shore.

Question 40

locations of these natural disasters

Answer 40

The Ring of Fire around the Pacific experiences:
• Around 90% earthquakes
• Around 75% volcanoes
in the world, because it is located along plate boundaries.

Question 41

impacts of volcanoes

Answer 41

• Death and destruction from lava, falling ash, fire, earthquakes associated with volcanic activity
• Changes to weather – acid rain, storms
• Volcanic winters from ash blocking light, leading to cooler, less predictable climate and crop failure
• Damage and disruption from fine ash particles to infrastructure eg. transport
• Very fertile soil – eruptions bring many nutrients to the surface eg. magnesium, potassium, phosphorus. Over time, weathering and erosion depletes soils of nutrients (which is why Australian soils are not fertile).

Question 42

impacts of earthquakes

Answer 42

• Tsunamis – Series of ocean waves caused by undersea earthquakes
• Landslides
• Volcanic eruptions

Question 43

Age, Stability and Lack of Volcanic/Earthquake Activity In Australia and How This Relates to the Location Away From Plate Boundaries

Answer 43

Australia currently sits in the middle of the Indo-Australian plate, meaning volcanic activity is very rare. However, there are many extinct volcanoes around Australia, some forming as the Australian plate moved over a hotspot, now thought to be near Bass Strait. Australia contains some of the oldest rocks in the world, with the world’s oldest known material – some grains of zircon – being found in Western Australia. These are 4.36 billion years old, nearly as ancient as the planet Earth itself. “Old” for rocks means it has not been changed by the rock cycle into a different type of rock. Therefore, the youngest rocks are formed by volcanoes. The age of the rocks in Australia is due to its location away from plate boundaries.