Plate Tectonics

Question 1

What are the 4 Layers of the Earths Crust

Answer 1

Crust, Mantle, Outer Core, Inner Core

Question 2

What is the composition of the Crust

Answer 2

Thin brittle layer that consists of the:
Continental Crust
Thicker (10 - 70km)
Rich in silicates and aluminium minerals

Oceanic Crust
Thin ( 5km), more dense and similar composition to basalt
Rich in Magnesium and silicate minerals

Question 3

What is the composition of the Mantle

Answer 3

Thickest layer of the earth (Average 2900 km thick)
Molten rock with convection currents in the upper mantle
High temperature and pressure
is primarily composed of silicate minerals rich in iron and magnesium

Question 4

What is the composition of the Outer Core

Answer 4

Liquid
Iron, Nickel and some lighter elements
Convection currents in the outer core may be responsible for the earth’s magnetic field

Question 5

What is the composition of the Inner Core

Answer 5

Solid due to high temperatures and pressures.
Mostly Iron with some Nickel

Question 6

What is evidence for the Continental Drift Theory

Answer 6

Fit of coastlines, similar fossils on separate continents, and the presence of ancient climate indicators similarities in rock formations and mountain ranges across continents, earthquake and volcano distributions align with plate boundaries, providing evidence for the movement and interaction of tectonic plates.

Question 7

What is the Continental Drift Theory

Answer 7

A proposed theory that the continents were once united into a single supercontinent named Pangaea. Suggests that that Pangaea broke up and moved long ago and this movement was driven by the gradual motion of tectonic plates on the Earth’s surface.

Question 8

What is evidence supporting the theory of plate tectonics

Answer 8

Evidence for plate tectonics: Continent fit, rock/fossil matches, seismic activity, earthquake/volcano patterns at plate boundaries, oceanic features (ridges, trenches).

Question 9

How does the location of earthquakes and volcanoes support the theory of plate tectonics

Answer 9

Earthquakes occur at plate boundaries due to plate interactions, like subduction or sliding.

Volcanoes emerge where plates separate or collide, allowing molten material to surface.

Divergent boundaries show volcanic activity and shallow quakes.

Convergent boundaries yield deep earthquakes.

Transform boundaries cause shallow but powerful quakes.

The consistent alignment of earthquake and volcanic activity with the locations of tectonic plate boundaries and their interactions provides strong evidence for the theory of plate tectonics.

Question 10

Why can volcanoes be found in the middle of a tectonic plate even if they are not on plate boundaries

Answer 10

volcanoes result from hotspots where magma rises through the plate from deep within the Earth, leading to volcanic activity even in the middle of tectonic plates.

Question 11

Why can earthquakes be found even if they are not on plate boundaries

Answer 11

Known as intraplate earthquakes, these earthquakes occur due to stress accumulation in weak zones within the Earth’s crust, resulting in sudden energy release despite not being directly associated with tectonic plate interactions.

Question 12

Explain why plate tectonics move in terms of heat and convection currents

Answer 12

Tectonic plates move due to heat-driven convection currents in the mantle. Hot, less dense mantle material rises and pushes plates apart at divergent boundaries, while cooler, denser material sinking drives plates together at convergent boundaries.

Question 13

Describe the process of subduction

Answer 13

Subduction is the process where a denser oceanic plate is pushed beneath a less dense plate at a convergent boundary. This leads to the formation of deep ocean trenches, volcanic arcs, and the recycling of Earth’s crust over long periods of time.

Question 14

How are ocean ridges formed?

Answer 14

Ocean ridges form where tectonic plates move apart. Hot mantle material rises through stretched crust, making magma. Magma erupts, cools, and forms new crust, building underwater mountain ranges. This process is seafloor spreading.

Question 15

Describe the theory of Seafloor Spreading and how it supports plate tectonics.

Answer 15

Seafloor spreading is a key part of plate tectonics. Hot mantle material rises at divergent boundaries, making magma that erupts, cools, and forms new seafloor. As this new crust forms, it pushes older crust away. This process helps explain the movement of tectonic plates and the creation of ocean ridges.

Question 16

What are the three types of plate boundaries

Answer 16

Divergent, Convergent and Transform

Question 17

Describe the characteristics and give examples of transform boundaries

Answer 17

These boundaries involve plates sliding past each other horizontally. The friction between the plates creates stress that’s eventually released as earthquakes. No new crust is created or destroyed at transform boundaries; no volcanoes.

San andreas fault

Question 18

Describe the characteristics and give examples of convergent boundaries

Answer 18

At these boundaries, plates move toward each other. Depending on the types of plates involved (oceanic or continental), one plate may be forced beneath the other in a process called subduction. This can lead to the formation of deep ocean trenches, volcanic arcs, and mountain ranges.

Question 19

Describe the characteristics and give examples of divergent boundaries

Answer 19

Here, tectonic plates move away from each other. Characterized by the formation of new crust as magma rises from the mantle to fill the gap, creating new crust. This process forms mid-ocean ridges and contributes to seafloor spreading. Examples:

Mid-Atlantic Ridge
Great Rift Valley
Red Sea Rift
Iceland

Question 20

Explain what a hot spot is and it’s significance

Answer 20

is an area of intense volcanic activity caused by a rising column of hot mantle material. It creates volcanic islands and chains away from plate boundaries, like the Hawaiian Islands, and offers insights into plate movement and the Earth’s internal dynamics.

Question 21

Describe the difference between continental and oceanic crust

Answer 21

Continental crust is thicker (Between 30 - 70km), less dense, and composed mainly of granite and sedimentary rocks. It forms the continents and is more stable. Oceanic crust is thinner (Avg 6 km thick), denser, and composed mainly of basalt. It forms the ocean floors and is more geologically active.

Question 22

Explain how palaeomagnetism can be used to support the theory of Seafloor Spreading.

Answer 22

Palaeomagnetism reveals Earth’s magnetic past in rocks. As new crust forms at mid-ocean ridges, rock minerals align with the magnetic field. Flips in Earth’s field create bands of normal/reversed polarity. Symmetrical magnetic patterns on both sides of ridges confirm plate movement and seafloor spreading theory.

Question 23

What is the shrinking Earth Theory and what predictions does it make about the locations of mountains, volcanoes and earthquake

Answer 23

The shrinking Earth theory suggests that our planet was once much larger and has been gradually contracting over time. This theory proposes that as the Earth shrinks, it causes the crust to buckle and fold, leading to the formation of mountains, volcanoes, and earthquakes.

Question 24

What is the Name of the scientist responsible for the Continental Drift Theory

Answer 24

Alfred Wegener

Question 25

Define Pangea

Answer 25

Pangaea was a vast supercontinent existing about 335 million years ago, comprising all the current continents fused together. Over time, tectonic forces led to its fragmentation into the continents we know today.

Question 26

Define Gondwana

Answer 26

Gondwana: Ancient southern supercontinent (around 335 million years ago) including present-day South America, Africa, Antarctica, Australia, Indian subcontinent, and Arabian Peninsula; later split into current continents.

Question 27

Define Laurasia

Answer 27

Laurasia was a northern supercontinent that existed around 335 million years ago, incorporating present-day North America, Europe, and Asia

Question 28

Define Panthalassa

Answer 28

Panthalassa was the vast global ocean that surrounded the supercontinent Pangaea during the late Paleozoic and early Mesozoic eras. It encompassed most of Earth’s oceanic area at that time and existed approximately 335 to 175 million years ago.

Question 29

What is a subduction zone

Answer 29

A subduction zone is where one tectonic plate sinks beneath another due to convergence. It causes geological activity like earthquakes, volcanoes, and mountain formation. Typically involves oceanic plates and generates features such as trenches and volcanic arcs.

Question 30

Characteristics of Convergent Boundaries (Continent to Continent)

Answer 30

Produce lots of earthquakes
Very little volcanoes
Continental Crust on both sides is light and resists subduction
Mountain Building

Question 31

Characteristics of Convergent Boundaries (Oceanic to Continent)

Answer 31

Subduction Zone Formation
Explosive Volcanic Activity
Earthquakes
Formation of Mountain Range

Question 32

Characteristics of Convergent Boundaries (Oceanic to Oceanic)

Answer 32

Subduction Zone Formation
Trench Formation
Explosive Volcanism
Earthquakes