Tectonic plates and Earth structure (1)

Question 1

What type of structure does the Earth have?

Answer 1

Layered

Question 2

Name and describe what it at the centre of the Earth

Answer 2

The Inner and Outer CORE

• Ball of solid and liquid iron and nickel
• Very dense at the centre, becomes less dense further out
• Temperature ranges from 4400-6000C

Question 3

Name and describe what is found around the core

Answer 3

The MANTLE

• Made up of silicon based rocks
• The part of the mantle nearest to the core is quite rigid
• The layer above this is the ASTHENOSPHERE - it id semi-molten
• Temperature ranges from 1000-3700C, cooler towards the Earth’s surface

Question 4

Name and describe the solid outer layer of the Earth

Answer 4

The CRUST

• Also made of silicon based rocks
• Two types of crust: continental and oceanic

Continental crust: thicker and less dense
Oceanic crust: thinner and more dense

• Divided into slabs called tectonic plates

Question 5

Why do tectonic plates move due to Convection currents?

Answer 5

(1) Tectonic plates float on the mantle

(2) Radioactive decay of elements in the mantle and core generates heat

(3) When lower parts of the asthenosphere heat, they become less dense and rise

(4) As the reach the top, they become cooler and more dense, slowly sinking

(5) Circular movements of semi-molten rock are Convection currents

(6) Convection currents in the asthenosphere create drag on the base of tectonic plates, causing them to move

Question 6

Name the 3 types of plate boundaries

Answer 6

Convergent (destructive)

Divergent (constructive)

Conservative

Question 7

Describe Convergent boundaries

Answer 7

• Where 2 tectonic plates move towards each other
• Oceanic plate meets a Continental plate, the denser Oceanic plate is forced downwards into the mantle and destroyed, creating COMPOSITE CONE volcanoes
• 2 Continental plates collide, folding the ground upwards, creating mountain ranges

Question 8

Describe Divergent boundaries

Answer 8

• Where 2 tectonic plates move away from each other
• Magma (molten rock) rises from the mantle to fill the gap, forming new crust and SHIELD volcanoes

Question 9

Describe Conservative boundaries

Answer 9

• Where 2 tectonic plates move sideways past each other, or moving in the same direction at different speeds

Question 10

Name the 2 types of volcanoes

Answer 10

Shield
Composite cone

Question 11

Describe Shield Volcanoes

Answer 11

• Occur at hotspots or divergent boundaries
• Not very explosive
• Erupt BASALTIC lava which has a low viscosity. It flows quickly over a wide area, forming a low, gentle-sided volcano

Question 12

Describe Composite cone volcanoes

Answer 12

• Occur at convergent boundaries
• Subducted oceanic crust contains lots of water, which reacts with magma, creating gases, causing the subducted crust to erupt
• Explosive eruptions that deposit a layer of ash
• Erupt ANDESITIC lava which has a high viscosity. The lava can’t flow far, forming a steep-sided cone

Question 13

What is a Hotspot?p and how are they formed?

Answer 13

Places where magma rises through the crust

• They occur where a plume of hot magma from the mantle moves towards the surface, causing an unusually large flow of heat from the mantle to the crust
• Sometimes, the magma can’t break through the crust, so an eruption, forming a volcano
• Hotspots remain stationary over time, but the crust moves above them, which can create chains of volcanic islands eg. Hawaii