Chapter 10 Flashcards
Wegener’s theory of continential drift.
The theory states that the continents were once bound, as a single continent. (Pangaea) (10.1)
Observations of Wegener which proved his theory’s validity. (10.1)
- The continents appeared to fit together, like a puzzle.
- Fossils of the same prehistoric species were found on the continents that were long apart. (10.1)
Seafloor Spreading
the process of new crust forming at the ocean ridges and spreading outwards. (10.1)
Tectonic Plate
Large sections of the crust that move about on Earth’s surface. (10.1)
Subduction
Where one tectonic plate is forced beneath another. (10.1)
Fault Line
A break or crack in Earth’s surface caused by shifting and moving plates.
Magnetic Striping
The patterns of magnetism trapped in rocks on each side of plate boundaries.
Subduction Zone
The region where an oceanic plate sinks down into the asthenosphere at a convergent boundary, usually between continental and oceanic plates (10.1)
Deep-Ocean Trench
A deep area along the ocean floor where oceanic crust sinks towards the mantle. It forms along a subduction zone (10.1)
Asthenosphere
A layer of ‘plastic’ semi-solid rock in the mantle.
Rifting
The process of continents breaking up and allowing in water from the sea. (10.1)
Fault
Cracks in the earth’s crust along which there is movement.
Support for Hess’ theory of seafloor spreading.
- Magnetic Striping
- Age of the seafloor
- Sediment thickness
(10.1)
Outline the two main observations that led Wegener to propose the theory of continental drift.
- The continents fit together, like a jigsaw.
- There were fossils of the same species on continents that weren’t connected.
Hot spot
An area where magma from the earth is hotter and in more quantity than normal. (10.3)
Pangaea
The name of the single landmass that comprised of all the continents. (10.1)
How did Wegener determine Pangaea’s appearance?
Wegener rearranged the continents so that the pieces of the jigsaw fitted and so the fossil distribution was continuous across the land masses. (10.1)
What are the 2 parts of pangaea?
Laurasia and Gondwana(land).
Which continents comprised Laurasia?
North America (Greenland), Europe, and Asia
you don’t have to know this; mark as 5 if you don’t want to
Which continents comprised Gondwanaland?
Antarctica, Australia, South America.
you only have to know Australia.
Describe three types of evidence that now supports the hypothesis of seafloor spreading. (know in detail)
- Rocks at a particular distance from the mid-ocean ridge on one side always had the same magnetic direction as rocks the same distance away
on the other side of the ridge. - The farther the rocks on the seafloor are away from the ridges, the older they are.
- Sedimentary rock layers on the ocean floor become thicker as you move away from the ridges.
(10.1)
Use the theory of plate tectonics to explain why Africa and America are older than the sea floor of the Atlantic Ocean.
New sea floor is constantly being created (seafloor spreading) but the continents were formed billions of years ago and very little land has been formed since then. (10.1)
Volcanoes
A volcano is a place where extremely hot molten rock (magma) from inside the earth erupts at weak spots (hot spots) in the earth’s crust. (10.1)
How does a volcano erupt?
Magma occasionally gets pushed to the surface of the earth and can then be identified as lava. (10.3)
Destructive Boundary
A place where crust (lithosphere) is being destroyed. (10.2)
Constructive Boundary
A place where new crust (lithosphere) is being created. (10.2)
What are the three types of plate boundaries?
Convergent/Collision (destructive), divergent (constructive), transform (10.2)
Convergent/Collision Boundary
A boundary where crust is destroyed by plates moving toward each other. (10.2)
Divergent Boundary
A tectonic plate boundary where crust is created by plates moving apart from each other. (10.2)
Transform Boundary
A plate boundary where two plates move past each other in opposite directions. (10.2)
Island Arc
A chain of islands formed at the edges of colliding tectonic plates where one plate subducts. (10.2)
What are the two types of crust that form the tectonic plates?
Oceanic and contienential crust. (10.2)
Continential Crust
The parts of the Earth’s crust that form the continents. (10.2)
Oceanic Crust
The parts of the Earth’s crust that makes up the ocean. It’s denser and heavier than continential crust. (10.2)
Ring of fire
[n/a]
Name one place where diverging boundaries are found.
Antarctic ridge between Australia and Antarctica. (10.2)
Name one place where converging boundaries are found.
Sunda trench between Australia and Indonesia.(10.2)
Name one place where transform boundaries are found.
The alpine fault of South Island New Zealand. SINZ (10.2)
Describe the process of subduction.
Subduction occurs either where a denser plate (oceanic crust) sinks under a lighter plate (continental plate) or a faster moving plate sinks below a slower moving plate. (10.2)
Why are transform boundaries not classified as destructive boundaries?
Because they do not destroy crust.
Fold Mountains
Mountains that form where two plates collide and force layers of rock into folds. (e.g. the Himalayas) (10.2)
Use plate movement to describe the origin of the Himalayas.
The Indian Plate is colliding with the Eurasian Plate. Because India and Asia are both light (continential) crust, they have been pushed upwards, forming the Himalayas. (10.2)
Which type of plate boundary does subduction occur in?
A denser plate (oceanic crust) converging with a lighter plate (continental crust). (10.2)
Which type of plate boundary do ocean trenches occur in?
Ocean crust subducts under continental crust. (10.2)
Which type of plate boundary do fold mountains occur in?
Where two continental crustal (light) plates collide. The continental plate becomes distorted, forming fold mountains and volcanoes. (10.2)
Which type of plate boundary does rifting under the sea occur in?
Rifting under the sea occurs where oceanic plates are separating (diverging). The land subsides in the centre and ridges form either side of the ‘crack’. (10.2)
Which type of plate boundary does an island arc occur in?
When two oceanic plates collide (converge) and volcanic activity creates a line of mountains. (10.2)
Which type of plate boundary does an ocean trench next to a continental mountain range occur in?
An oceanic plate collides (converges) with a continental plate and subducts below the continent. (10.2)
Iceland is extremely volcanically active and is growing at 2-5 cm a year. Explain how these two facts are linked.
Because a diverging boundary runs through the island. New crust is created and this adds about 2-5 cm of land a year. (10.2)
Compare subduction when two ocean plates converge with subduction when an oceanic and continental plate converge.
When two oceanic plates converge, the faster moving one is subducted underneath the slower.
When an oceanic and continental plate converge, the continental is subducted underneath the oceanic, as it’s less dense and lighter.
(10.2)
Earthquake
The rapid movement of the ground in a wave motion, due to the movement of tectonic plates. (10.3)
Island Chain
A series of volcanic islands with only one active volcano at the end of the chain. (10.3)
Seismometer/Seismograph
An instrument that detects the seismic waves from an earthquake. (10.3)
Volcano
A weak spot in the Earth’s surface through which magma and gases are expelled. (10.3)
Epicentre
The point on the Earth’s surface directly above the focus of an earthquake. (10.3)
Seismic Waves
The shaking, wave-like movement of the ground in an earthquake. (10.3)
Lava
Molten rock that has erupted onto Earth’s surface. (10.3)
Magma
Molten rock that is beneath the Earth’s surface. (10.3)
Name a tectonic process that generates heat at the boundaries of the plates.
Subduction. (10.3)
Explain how island chains form from hot spots below the ocean crust.
Each island forms as it sits over the hot spot.
As the plate moves, the island goes with it.
A new part of the plate is now above the hot spot and this gradually forms a new volcano. Gradually, a chain of islands forms.
Explain the cause of earthquakes.
Earthquakes are caused by the rapid release of energy as the tectonic plates move. This sudden movement sends out waves of energy through the rock and water. (10.3)
How could you tell if a line of islands was formed by a hot spot and tectonic plate movement?
Check how many of the volcanoes in the chain are active. If it is only one, there is a good chance it is a hot spot volcano.
How many volcanoes are active in an island arc?
Commonly one, as it’s the last island to form.
Explain why Australia is a geologically stable continent.
The lithosphere is very thick—more resistance to being melted and fractured by earth movements. The continent is not near plate boundaries so fewer earthquakes and volcanoes occur. (10.3)
Explain why Japan has many active volcanoes, whereas Australia has none.
Japan is on a collision boundary between a subducting oceanic plate and a continental plate; these collision boundaries usually have lots of volcanoes because they generate a lot of magma.
Australia is well away from subducting plate boundaries or diverging plate boundaries, so there is no
volcanic activity.
(10.3)
Describe 2 ways GPlates helps (generally and in mining)
It creates images of tectonic plates and other geological features and allows you to manipulate that and changes over time. (10.1)
What happens when molten rock solidifies?
All the magnetic particles in it line up with Earth’s magnetic field to point in the same direction.
Explain the process of magnetic striping.
See fig. 10.1.6
Draw a diagram of a convection current.
See fig. 10.1.9.
