Hazardous Earth

Question 1

What are Plate Tectonics?

Answer 1

Plate tectonics is the scientific theory that Earth’s lithosphere comprises a number of large tectonic plates, which have been slowly moving since about 3.4 billion years ago.

Question 2

Jigsaw fit

Answer 2

Some continents fit together like a geological jigsaw
puzzle. All the rocks were formed when the land was a single continent – Pangea.

Question 3

What was the one big large mass called created by Alfred Wegner?

Answer 3

Pangaea

Question 4

What is Continental drift?

Answer 4

The idea that continents are slowly shifting their positions

Question 5

Convection currents

Answer 5

In the Mantle, Convection Currents were found to be slow yet extremely powerful
movements of volcanic rock in the mantle. The magma is heated to 50000C in the
mantle and rises to the crust where they cool and sink only to be heated again. The
process continues. This was powerful enough to move the earth’s plates.

Question 6

Study of fossils

Answer 6

Similar fossils are found on different continents. This is evidence that these regions
were once very close or joined together. Such species could not have crossed
oceans, so they must have lived on the same land mass at some time in the past.

Question 7

Where was the bones of the reptile Mesosaurus found?

Answer 7

The bones were forund in southern Africa and the southern part of South America.

Question 8

Geological patterns

Answer 8

Similar pattern of rock
layers on different
continents is evidence that
the rocks were once close
together or joined.

Question 9

Oceanic crust

Answer 9

plate that is made up of more dense rock. It sinks easily due to its
density and is constantly created at boundaries. It is ‘young/new
rock’ and forms our ocean bed.

Question 10

Subduction zone

Answer 10

where one plate is forced downwards below another plate and
grinds past it causing huge amounts of friction and heat.

Question 11

Destructive plate boundary

Answer 11

where two plates are moving towards each other, one of which is
continental crust and one is made of oceanic crust

Question 12

Continental crust

Answer 12

this is a plate that is made up of less dense rock. Because it is less
dense it doesn’t sink. It is exceptionally old and makes up our land
surfaces.

Question 13

Plate boundary

Answer 13

where two very large crustal plates meet on the earth’s surface.
Earthquakes and volcanoes happen here.

Question 14

Fold mountains

Answer 14

are large mountain ranges formed by the collision and ‘folding’
of two plates as they plates continually push into one another.

Question 15

Ocean trench

Answer 15

a particularly deep point of the ocean bed where the oceanic and
continental crust have dragged each other downwards.

Question 16

Composite volcano

Answer 16

a very steep
volcano which is formed at a
destructive boundary. The
magma under the surface has
high silica and is very explosive –
these are the most dangerous
volcanoes.

Question 17

Pyroclastic flows

Answer 17

fast-moving currents of hot gas and rock, which reaches speeds moving
away from a volcano of up to 450 mph. The gas can reach temperatures of about 1,000 °C.
Pyroclastic flows normally hug the ground and travel downhill, or spread laterally under gravity.

Question 18

Volcanic bomb

Answer 18

a mass of molten rock larger than 64 mm in diameter, formed when
a volcano ejects viscous fragments of lava during an eruption.
Volcanic bombs can be thrown many kilometres from an erupting vent, and often acquire
aerodynamic shapes as they cool during their flight. The largest have been evidenced in
Japanese eruptions, up to 6 metres in diameter.

Question 19

Lahars

Answer 19

Lahars are when a snow-capped volcano erupts, melting the snow and ice.

Question 20

What is an earthquake?

Answer 20

Earthquakes are vibrations of the Earth’s crust caused by movement at
plate boundaries and major fault lines.

Question 21

Where do earthquakes occur?

Answer 21

Earthquakes can occur at all major fault boundaries but the most
severe are usually conservative and convergent.

Question 22

Epicentre

Answer 22

The point on the ground above where an earthquake
happens

Question 23

Focus

Answer 23

The point along the fault in
the crust where an earthquake
happens

Question 24

Fault line

Answer 24

A line on the earths surface that traces a
geological fault.

Question 25

Stress and release

Answer 25

When pressure builds between two plates stress
is placed on the fault line. When the stress builds up
too much it is released.

Question 26

Shockwaves

Answer 26

Powerful shockwaves are released from the
focus. Primary waves travel forwards and
backwards and move quickly.
Secondary waves are slower and move sideways and
up and down.

Question 27

Richter scale

Answer 27

measures the magnitude of
the earthquake (how much the ground
shakes)

Question 28

Mercalli scale

Answer 28

measures the intensity of
the earthquake (based on observations of
the resulting damage)

Question 29

What do you use to measure the magnitude of a tremor using!

Answer 29

An instrument called a seismometer.

Question 30

What is a primary effect of an earthquake?

Answer 30

Something that happens in the short term by the earthquake

Question 31

What is a secondary effect of an earthquake?

Answer 31

Something happening in the long term as a result of a primary effect

Question 32

Supervolcano

Answer 32

a volcano 1000x times bigger than a regular volcano that has the
potential to produce an eruption with major effects on the global climate and ecosystems.

Question 33

What are tsunamis normally triggered by?

Answer 33

Eathquakes