Natural Disasters

Question 1

What type of rocks is the continental crust formed from?

How about the oceanic crust?

Answer 1

Granite

Basalt

Question 2

Describe P waves

Describe S waves

Answer 2

P waves move faster and can travel through solids and liquids (longitudinal wave which arrives first)

S waves move slower and cannot travel through liquids (arrives second but causes much more damage)

Question 3

Describe convergent, divergent and transform plate boundaries

Answer 3

Convergent is when the tectonic plates come together

Divergent is when the plates move apart

Transform is when the plates slide at a cross section from each other

Question 4

Describe what happens on an Oceanic-Convergence boundary

Answer 4

Oceanic plate subducts underneath the continental plate

Lots of earthquakes and volcanoes and tsunamis occur

Question 5

Describe what happens on an oceanic-oceanic convergence

Answer 5

Trenches are the main forming item, strong earthquakes and volcanos occur

Island arcs are formed

Question 6

Describe what happens on a continental-continental convergence

Answer 6

When two continents meet head on, neither is subducted. The crust pushes upward or sideways forming mountains

Question 7

What happens at the ring of fire

Answer 7

The most geologically active region of earth

The majority of earths major earthquakes, and volcanos occur here

Question 8

Describe a divergent plate boundary

Answer 8

Plates move apart
Crust is created here (sea floor spreading)
Volcanos are common here

Question 9

What happens on a transform plate boundary (strike-slip fault)

Answer 9

The plates are sliding past one another

Very few occur on land most are found on the ocean floor

Question 10

What is the epicentre vs focus

Answer 10

The epicentre is the point in the earths surface vertically above the focus (point directly above the focus on the surface of the earth)

The focus is the exact point in the earth where the rupture starts

Question 11

What is the Richter scale and how is magnitude measured?

Answer 11

Logarithmic scale and therefore each order of magnitude increase is a tenfold increase

Magnitude 2 quake is 10 times more ground movement than magnitude 1

Question 12

How is a tsunami formed

Answer 12

When fault movements of the sea floor result in uplifting or down dropping seabed, produces earthquake of at least 7.5

Question 13

Describe an earthquake at a subduction zone

Answer 13

A thrusting motion of mega thrust earthquake causes large vertical movement on the sea floor and this displaces a large volume of water causing a tsunami

Question 14

Describe an earthquake on a divergent plate boundary

Answer 14

Earthquakes are almost always less than 10km deep and are typically small in magnitude

Question 15

Volcanoes in subduction zones

Answer 15

Typically cone shaped stratovolcanoes,

Blocky, viscous lava rich in silica

Commonly erupt violently to form viscous lava flows

Magma generated when water in descending Oceanic crust is driven out and rises to the mantle

Question 16

Volcanos on divergent plate boundaries

Answer 16

Characterized by fissure eruptions when the ground splits apart

Question 17

What are the 3 layers of earth

Answer 17

Crust

• continental
• oceanic

Mantle

• upper mantle
• lower mantle

Core

• outer core
• inner core

Question 18

Describe hotspot volcanism

Answer 18

When lava former deep inside the mantle, forms a plume that rises from the centre of the earth and rises to the surface, when the lava rises to the surface it hits the water and forms land

In Hawaii the magma plume forms islands and as the ocean floor moves the islands form in a line