science term 1

Question 1

What is the theory of plate tectonics?

Answer 1

plate tectonics are a combination of 2 theories: continental drift & seafloor spreading

Question 2

What is continental drift?

Answer 2

The idea that continents is continuously moving and have significantly changed positions over millions of years.

Question 3

What is sea floor spreading?

Answer 3

Seafloor spreading proposes that the middle of the ocean is spreading apart, moving very slowly in opposite directions.

Question 4

Who proposed the theory of continental drift?

Answer 4

Alfred Wegener

Question 5

Who proposed the theory of seafloor spreading?

Answer 5

Harry Hess

Question 6

What is the evidence of continental drift?

Answer 6

• the similarities in shape between the coastlines of Africa and South America. they fit together like puzzle pieces.
• Alfred Wegener proposed that they all fit together into a giant continent called Pangea
• The coastlines fit similar fossils, rocks and landforms created by glaciers in now widely separated continents

Question 7

What is the process of seafloor spreading?

Answer 7

evidence came from discovery of the mid Atlantic ridge

• If convection occurs within the earths mantle, then rising hot magma pushes up, creating a ridge crest.
• It is pushed to one side by more rising magma and the ridge splits and moves apart.
• As it is pushed away, tension between the surrounding rocks causing a rift zone and shallow earthquakes. As the mantle rock moves away from the ridge crest, it carries the sea floor with it.

Question 8

what are the main forces that cause plate movement?

Answer 8

slab pull, ridge push, gravity and convection currents

Question 9

What is slab pull?

Answer 9

Largest force in plate movement. When 2 plates come together, one is pushed under the other called a ‘subduction zone’. The subducted plate continues to sink. Gravity pulls the front of the plate down causing it to move

Question 10

What is ridge push?

Answer 10

When 2 plates move apart, magma from the mantle rises up to fill the gap and forms a raised ‘ridge’ in the ocean floor. As this ridge is hot and heavy it expands and pushes the rest of the plate away from the ridge, causing it to move

Question 11

What is convection?

Answer 11

Movement of matter within a fluid. Hotter and therefore less dense material to rise. Colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat. Occur in earth’s upper mantle.

Question 12

Convection Currents in plate movement

Answer 12

With the hot rocks rising and the cooler rocks sinking due to gravity, it causes friction between the movement of rocks and the plate tectonics which can lead to movement

Question 13

What are the major plates on a world map?

Answer 13

Eurasian
Australian
Antarctic
Pacific
North American
South American
African

Question 14

What are Diverging Plate Boundaries?

Answer 14

Plates moving away from each other
A gap forms, Valley forms and mountains may form on outside and streams and rivers may form in a rift, New tectonic plate may form is fully break away, Oceanic to Oceanic: When 2 oceanic plates move apart it is seafloor spreading.

Question 15

What are transforming Plate Boundaries?

Answer 15

Grind past each other
Causes a fault/crack in earth’s crust. EG: san andreas
Earthquakes are common

Question 16

What are 3 Landforms that typically occur at each boundary?

Answer 16

Volcanoes
Mountains
Narrow lakes or seas

Question 17

what is the evidence of theory of plate tectonics?

Answer 17

Oceanic plate is newer near oceanic ridge indicating plate moving away from ridge.
More sediment on oceanic plate near continental plate. Sonar survey by Harry Hess showed ridge existed