Topic 1 - Earth Structure + Volcanos/tsunamis (set B)✔️

Question 1

What is the lithosphere/crust ?

Answer 1

Crust is the surface of the earth and is split into tectonic plates made up of silicon based rocks

Question 2

What is the astenosphere?

Answer 2

Upper layer of the mantle - semi molten

Question 3

what is the mantle?

Answer 3

Largest part of the earths layers - made of silicon based rocks - part nearest to the core is quite rigid - temp of mantle between 1000 and 3700 degrees

Question 4

What is the inner core?

Answer 4

Very dense centre with temps of 4400 to 6000 degrees - made of iron and nickel

Question 5

What is the outer core?

Answer 5

Less dense then the inner core and is made of liquid iron and nickel - temp 4500 to 5500 degrees

Question 6

What are the two types of earths crusts? what are there features?

Answer 6

-continental crust - 30 to 50km thick and less dense mostly made of granite

-oceanic crust - 6 to 8 km thick and light but dense and made of basalt

Question 7

Why do tectonic plates move?

Answer 7

Tectonic plates always moving due to convection currents in the mantle

Question 8

Explain the process of convection currents in the mantle?

Answer 8

Radioactive decay of elements in the mantle generates lots of heat - lower parts of the mantle heat up and become less dense and slowly rise - they cool down and become more dense and slowly sink - drags on base of tectonic plate and causes movement

Question 9

What fuels convection currents?

Answer 9

Radioactive decay of elements like uranium and thorium in the mantle and core

Question 10

What happens at convergent boundaries?

Answer 10

1)Oceanic plate meets a continetal plate and oceanic is submerged into the mantle and destroyed often creating volcanos and ocean trenches

2)continenetal plate meets continental no subduction - they collide forming fold mountains

Question 11

What are plate boundaries?

Answer 11

Where tectonic plates meet creating three types of boundarys

Question 12

Products of convergent boundaries?

Answer 12

• fold mountains
• composite volcanos
• ocean trenches

Question 13

What happens at divergent boundaries?

Answer 13

Two plate move away from each other - eg at mid Atlantic ridge - magma rises from the mantle to fill gap and cools creating new crust

Question 14

Product of divergent boundaries?

Answer 14

New crust formed
Underwater shield volcanos formed

Question 15

What happens at conservative boundaries?

Answer 15

Two plates moving sideways past each other in the same direction - they become stuck and pressure builds up until plate can break free causing earthquakes - crust is not created or destroyed

Question 16

Products of conservative boundaries?

Answer 16

Earthquakes

Question 17

Where do composite volcanos occur?

Answer 17

Occur at convergent plate boundaries - subducted oceanic contains lots of water which reacts with magma and creates gasses which causes subducted crust to erupt

Question 18

Features of composite volcano?

Answer 18

• explosive eruptions and deposit a layer of ash
  -erupt andesitic lava which has a high silica content which makes it thick and sticky cant flow

Question 19

Features of shield volcanoes?

Answer 19

• occur at hotspots or divergent plate boundaries
• not very explosive made up of only lava
• erupt basaltic lava which has low silica content and is runny - flows quickly and spreads

Question 20

What is the structure and features of andesitic lava?

Answer 20

• high silica content makes it thick and sticky and can not flow far

Question 21

What is the structure and features of basaltic lava?

Answer 21

Has a low silica content and is runny - flows quickly and spreads over a wide area

Question 22

Where do shield volcanos form?

Answer 22

Occur at hotspots or divergent plate boundaries

Question 23

How do hotspot volcanos form?

Answer 23

Occur where a plume of hot magma from the mantle moves towards the surface which can break through the crust and reach the surface causing an eruption and a shield volcano forming - hotspots remain stationary but crust moves above them which creates a chain of volcanic islands

Question 24

How was Hawaii formed?

Answer 24

Is a chain of volcanic islands in the middle of pacific plate cause by hotspots and the crust moving above them

Question 25

What is a tsunami?

Answer 25

Series of ocean waves usually created by volcanic or earthquake activity under the ocean can reach over 30 m high

Question 26

how do tsunamis form? What happens just before they hit?

Answer 26

When an earthquake or volcano happens on the ocean floor it displaces water - which once it reaches shallower water begins to slow down and grow in height - hard to detect but coastal water starts to retreat just before wave hits coast