Earth Flashcards
(20 cards)
Transform boundaries
Two plates slide along a fault line.
Stop and slide, as pressure builds up.
No material created or destroyed
Can cause dramatic earthquakes.
Eg. San Andreas fault line N-American and Pacific Plates.
Layers of Earth
Solid metal inner core
Molten rock outer core
Thickest part mantle
Thinnest part Crust or lithosphere
What are tectonic plates
Large pieces that the crust is broken into,
They float on semi-liquid magma at the top of mantle.
Land masses and oceans can exist on the same plate
Sea-floor spreading
Discovered Mid-Atlantic Ridge
Convection currents within mantle leads to rising magma creating ridge crest. Current causes ridge to split and sea-floor to move apart.
Rock cools and becomes denser. New land is formed.
Continental drifting
Alfred wegener, early 1900s
In the past all continents fit together into one land mass=Pangaea
Based on complimentary shapes of continents.
Somewhat supported-> similar species, landforms and fossils found in separate countries.
BUT NOT CONTINENTS, TECTONIC PLATES.
Australia and tectonic plates
Middle of Indo-Australian plate.
Not at plate boundary, so there aren’t many earthquakes or volcanoes.
The Indo-Australian plate grinds upwards into the Eurasian plate to form the Himalayas.
Ring of Fire
On the edge of the Pacific Plate. New Zealand, Chile, Indonesia, Alaska, Japan. Caused some of most severe earthquakes Eg. Tohoku in Japan Aceh in Indonesia.
Ocean-to-ocean converging boundaries
Hawaiian islands
Red Sea
When diverging boundaries create wide oceans
Himalayas
Subduction
Indo-Australian and eurasian plate
I-A Plate moves up into Eurasian Plate
Earthquakes at the ring if fire
Aceh in Indonesia
Tohoku in Japan
San Andreas Fault !ine
Created by transform boundary
North American and Pacific Plates.
Ocean-to-continent converging boundaries
Andes
Nazca Plate and South American Plate
Continent-to-continent converging boundaries
Himalayas
Indian Plate and Eurasian Plate
Describe ocean-ocean collision
The older and denser oceanic crust subducts below the newer, and creates a deep ocean trench.
Lines if undersea volcanoes can also be created, that MAY reach above the water’s surface and create a chain of islands.
Describe ocean-continent collision
Oceanic crust subducts under continental.
Creates a line of mountains along the edge of the two plates. The heat and magma rising up through cracks in the crust create volcanoes.
An ocean trench is formed, just like in ocean-ocean collisions.
Describe continent-continent collision
The two crusts would have similar densities, so any subduction that occurs would be based on which one is denser. Otherwise, the plates crumple and fold into high mountain ranges.
Earthquakes caused by
A sudden release in pressure between two boundaries.
Transform boundaries especially can cause dramatic earthquakes.
Tsunamis are created by…
Undersea earthquakes move the sea floor and push up water, which forms a wave. Tsunami waves are shallow and travel at high speeds across oceans. When they reach continents, the wave can reach more than 10m high!
Violent volcanic eruptions can also create tsunamis.
What happens at a diverging boundary?
Diverging boundaries can occur either under land or sea. It is thought that the cause for this is the rising mantle rock under plates. The crust lifts and thins out, causing cracks to appear. Large slabs of rock sink down and form RIFT VALLEYs.
A sea or a lake could form between the separated continental crust and eventually create an ocean. A mid-ocean ridge would wind it’s way around the middle of the oceans. It is very wide, as the sea-floor spreads by about 5cm per year. The ocean floor is never very old, because of subduction and the creation of new ocean floor from rising and cooling magma. Because of the magma pushing up through cracks, diverging boundaries are often associated with underwater volcanic activity.
