The Restless Earth Flashcards
Name the 4 layers of the Earth
Inner core
Outer core
Mantle
Crust
Name the two main types of crust
Oceanic and continental
What are the characteristics of the oceanic crust
Very dense
Thin 5-10km
Can sink into mantle
Easily destroyed
Young crustal material
What are the characteristics of the continental crust
Less dense (lighter)
Thick 30-70k
Does not sink easily into mantle
Hard to destroy
Old crustal material
What is the plate tectonics theory
Proposes that the earths crust is split into sections called tectonic plates. Plates move around on top of the mantle. The places were plates meet, called plate margins are related to seismic and volcanic activity
Why do plates move
Convection currents
The earths core is extremely hot, causes rock in mantle to melt and form magma
Magma closest to the core is hottest and less dense than magma above it.
Therefore rises towards earths surface
As it moves further away from the core it cools down becoming less dense and sinking again
As this magma cycles around and moves the plates move with it
This process repeats moving the plates
Name 4 plate margins
Constructive - plates are pushed apart so move away from each other and new crust is created
Destructive- oceanic plate crashes into another plate and oceanic crust is pushed into mantle and destroyed
Collision- where two sections of continental crust crash into each other and both are pushed upwards to form a vast mountain range.
Conservative- where plates slide past each other. Crust in neither created or destroyed.
Process landforms and examples of constructive plate boundary
Plates move away from each other due to convection currents
This creates a gap between plates
New magma from the mantle rises up to fill gap
The rising material causes crust to rise slightly at either side of paste margin creating a mid ocean ridge. Underwater shield volcanoes may be formed and grow with each eruption creating islands.
Example, mid Atlantic ridge
Process, landforms and examples of destructive plate boundary between oceanic and continental plates.
Plates move together due to convection currents
Heavier more dense oceanic plate is forced underneath the lighter continental plate (subduct), this creates a deep ocean trench e.g Peru chile trench
This area is called a subduction zone as the movement between plates is not smooth friction builds up causing earthquakes.
The heat from the mantle can melt oceanic crust that is sinking which quickly turns into magma.
Magma is less dense so rises to the surface as an explosive form of magma. If it breaks through the surface volcanoes can be created causing eruptions.
As plates are pushed together it can create fold mountains e.g Andes mountain range.
Process landforms and examples of destructive oceanic plates boundary
More dense or heavier oceanic plate sinks below into mantle
This creates a deep ocean trench.
Magma the rises upwards may erupt through crust to create a volcanic island. Islands arc aligned to plate boundary
Collision boundary process, landforms and examples
Two continental crust plates are forced together by convection currents. Plates have similar densities so neither is forced under therefore the plates push each other and crumple and fold upwards.
This creates high mountains called fold mountains. No material melting so no volcanoes, but there are earthquakes.
Indian plate and Eurasian plate collision caused the formation of the Himalayas.
Conservative plate boundary process, landforms and examples
Plates slide past each other. As they pass the plates get stuck, friction and pressure builds until eventually the plates jerk free causing an earthquake. This also happens if the plates are moving in the same direction but move at different speeds.
As crust is neither created or destroyed there or no volcanoes
Example of conservative plate margin: San Andreas fault in California.
Name 3 main rock types
Igneous
Sedimentary
Metamorphic
How are igneous rocks formed?
Molten lava or magma cools and hardens.
If lava is exposed on surface it will cool quite quickly producing few if any crystals.
If the igneous rock is made from magma that cools slowly underground, then large crystals may form.
What are examples of igneous rocks in NI.
The giants causeway- basalt
The Mournes- granite
How are sedimentary rocks formed
Rocks are constantly worn down by rain, wind and sun to create tiny grains of clay, mud or sand.
This sediment is washed into rivers, lakes and oceans.
They sink and settle to the bottom of the water.
Over time layers build up
The sediment is forced together by a process called compression this when the weight of water forces all air and moisture out over time.
Eventually this process forms solid rock.
What are examples of sedimentary rock in NI
Strabo tower - sandstone
Marble Arch caves- limestone
Siltstone
Mudstone
How is limestone formed?
Limestone is made when after millions of years of skeletons of marine creatures and ear plants become sediment on the sea floor and compress due to weight of water. This forms limestone (calcium carbonate). Some plants and animal skeletons remain as fossils
How is a metamorphic rock formed
Metamorphic rocks are rocks that have been changed by extreme heat of pressure. They are rocks that were once either igneous or sedimentary.
Examples of metamorphic rocks and where are they found in NI
Limestone turns to marble
Shale turns to slate
Found in Tyrone and Londonderry
Characteristics of granite
Very hard
Dark grey
Rough and heavy
Few crystals
Characteristics of limestone
Grey or white rock
Fossils and sea creatures skeletons visible
Porous
Characteristics of sandstone
Granular
Layers
Soft
No crystals
Characteristics of slate
Dark grey
Easy to split
Smooth surface
Characteristics of marble
Pure white
Unpolished
Crystals
What are earthquakes
The shaking of the ground surface caused by sudden movement of the earths crust
Where do earthquakes mostly occur
Encircle the Pacific Ocean (ring of fire)
Along coast of Mediterranean Sea through Southern Asia towards pacific
The middle of Atlantic Ocean
Define focus of earthquake
The point out origin of an earthquake under the earths surface. Seismic waves spread from this point
Define epicentre of earthquake
The first place on earths surface to feel shockwaves from earthquake. This point is directly above the focus
What is the Richter scale
A logarithmic scale of 1-10 which measures the strength or magnitude of earthquake
What are physical consequences of earthquakes
Tsunamis and liquefaction
Define tsunami
A tsunami is a large wave of seawater generated by an underwater earthquake. The seismic waves from the plate movements create small waves (30cm). These small waves can travel for thousands of miles. As they approach the coast they become much taller (30cm)
Define liquefaction
Liquefaction happens when rock or soil containing water is shaken by an earthquake. As the ground shakes during an earthquake the water rises to the surface and turns the solid material to liquid mud. As a result, buildings can sink into this material.
What are volcanoes
Volcanoes are mountains often cone shaped, formed by surface eruptions of magma from inside the earth. During the eruption lava, ash, gas and rock will be released.
Name 2 types of volcanoes
Shield volcanoes and composite volcanoes
Characteristics of shield volcanoes
Large wide cone shaped. Gentle slopes made from runny lava
Cover a large area and occur at constructive plate boundaries
Have frequent eruptions which are more gentle and non violent in nature.
Characteristics of composite volcanoes
Classic mountain shaped
Made from hardened layers of ash and lava created after each eruption
Occur at destructive plate boundaries and have common features such as high cone, main and secondary vents
What is a super volcano
A type of volcano where the potential exists of it erupting at least 1000km3 of material, having global consequences.
Characteristics of super volcanoes
Wide depressions called calderas with a ridge of high land encircling them.
Forms when a volcano erupts so violently that it collapses in on itself covering magma chamber in layers of rock. Magma and pressure build up overtime ending in a violent eruption.
