Ch 1.1 Why is our earth unstable?

Question 1

What is a hazard?

Answer 1

A hazard is an event that threatens or cause loss of life and property.

Question 2

What are the examples of tectonic hazards?

Answer 2

Earthquakes, volcanic eruptions and tsunamis.

Question 3

What is the structure of the earth?

Answer 3

Crust, mantle and core.

Question 4

What is the composition of crust, mantle and core?

Answer 4

Crust - Continental crust - silica and aluminium.
- Oceanic crust - silica and magnesium.
Mantle - Rich in iron and magnesium.
Core - Rich in iron and nickel.

Question 5

How does the density of the layers changed?

Answer 5

It increases from the crust to core which means crust has the lowest density and core has the highest density.

Question 6

What makes up the continents and continental shelves?

Answer 6

continental crust.

Question 7

Name the characteristics of continental crust.

Answer 7

Continental crust is thick and less dense. The age of rock is old.

Question 8

Name the characteristics of oceanic crust.

Answer 8

Thinner and denser. The age of rock is generally younger than continental crust.

Question 9

What are the parts of the mantle?

Answer 9

Solid uppermost part of the mantle, plastic asthenosphere, solid lower mantle.

Question 10

How is the lithosphere formed?

Answer 10

The uppermost part of the mantle together with the crust form the lithosphere.

Question 11

What state is asthenosphere in and how do they flow?

Answer 11

The rocks in this layers are in plastic state and they can flow very slowly under pressure.

Question 12

What state is lower mantle in?

Answer 12

It exists in solid state under high pressure.

Question 13

What is core?

Answer 13

It is the hottest and densest part of the earth.

Question 14

What parts of core there are ?

Answer 14

Outer core and inner core.

Question 15

What is outer core?

Answer 15

It is very hot. The material has melted and is in liquid form.

Question 16

What is inner core?

Answer 16

It is under the greatest pressure. The material is kept in solid form.

Question 17

What are the types of plate boundaries?

Answer 17

Divergent plate boundary, convergent plate boundary, transform plate boundary.

Question 18

Name the characteristics of divergent plate boundary.

Answer 18

1. Plate diverge or move apart.
2. New crustal material is formed.

Question 19

Name the characteristics of convergent plate boundary.

Answer 19

1. Plates converge or move towards each other.
2. The denser plate sinks or subducts into the asthenosphere and is destroyed.

Question 20

Name the characteristics of transform plate boundary.

Answer 20

1. Plates slide horizontally past each other.
2. No crystal material is formed or subducts and is destroyed.

Question 21

Why do plate move?

Answer 21

Plate movements are driven by gravity, like denser materials must sink whereas less dense materials must rise.

Question 22

What types of mantle convection are there?

Answer 22

Rising convection currents, sinking convection currents.

Question 23

What is rising convection currents?

Answer 23

Rock in the lower mantle is intensely heated up by the core. Heated mantle rocks rise, become mantle plumes and rise as mantle plume to the cooler region of the upper mantle. New oceanic lithosphere is formed.

Question 24

What is sinking convection currents?

Answer 24

The newly formed oceanic lithosphere becomes older. It cools, contracts become denser and sinks.

Question 25

What is ridge push?

Answer 25

1. The mantle plume thrusts itself into the lithosphere above and causes the lithosphere to fracture and creates fissures. Pressure on the asthenosphere reduces and this lowers the melting point, thus producing magma.
2. Hot magma rises and fills the fissures to form new crustal materials. They even rise above the existing crust and form an up-swelling ridge.
3. Materials cool off, solidify and become new parts of the lithosphere. Its density increases and slides down from the two sides of the ridge under the force of gravity. The older lithosphere is pushed away from the ridge.

Question 26

What is slab pull?

Answer 26

1. The old lithosphere continues to move away from the ridge, it merges with some of the rock materials in the asthenosphere, and gets thicker in process. They become a dense, heavy slab of plate.
2. When it collides with another plate, it sinks into the asthenosphere. This creats a suction force that pulls the rest of the plate behind it.