Yr9 Science Revision - Earth and Space

Questão	Responda
What is the Lithosphere?	made up of the crust and the upper solid part of the mantle where we live
What is the Asthenosphere	A layer of 'plastic' semi-solid rock, that can flow very slowly and is very hot that they tectonic plates float on
What are the 2 theories of how the tectonic plates move?	Convection Currents and Gravity
Types of tectonic plate movements	Diverging, Converging and Transform
Convection Currents Theory	The plates are dragged along as the hot magma in the asthenosphere rises up and then flows horizontally under the plates until it cools and then sinks again. The friction between them may be enough to move it.
Gravity Theory	Gravity pulls the new crust away from the ridge as it cools and becomes denser.
What did Alfred Wegener discover about the tectonic plates?	They fit together like a jigsaw puzzle
What was Alfred Wegener's theory? (Continental Drift)	That the continents were once connected together in one landmass and that they must have drifted apart. he called this Continental drift
What was the large landmass called before the continents split apart?	Pangea
What were Wegener's 2 observations	1) The continents seemed to fit together like a jigsaw 2) Fossils of the same species were found on continents that were far apart
What did Harry Hess discover?	The Great Global Rift system
What is the Great Global Rift System?	A series of flat-topped mountains un the Pacific Ocean
Where are rifts found?	Diverging plate boundaries (plates that pull apart)
Seafloor Spreading	As tectonic plates move away from each other hot magma rises through the gap between them then solidifies when it hits the seawater forming new crust
Subduction	The process of crust sinking down which causes 1 plate to sink under another when they converge
What does subduction occur at oceanic - continental or oceanic - oceanic	Ocean Trenches
Where can you find the older oceanic crust from seafloor spreading?	The crust that is furthest away from the ridge is the oldest
Evidence of Seafloor Spreading	layers of the sedimentary rock on the ocean floor became thicker as you move away from the ridges meaning they had been falling for a longer amount of time
Diverging Plate Boundaries	occur when two plates are moving apart from each other
What do Diverging Plate Boundaries form? Give Example	Mid-ocean trenches - can occur on land or in water. When they separate it creates a rift (deep crack) between them and magma then rises through the crack and solidifies. Because they form new crust they are known as constructive boundaries Eg) Iceland
Converging Plate Boundaries	When 2 plates collide
3 types of converging plate boundaries	continental - continental oceanic - oceanic oceanic - continental
Density - Which is denser oceanic or continental?	How closely packed the particles are in a substance. Oceanic crust is denser than continental. an object will float if it is less dense than the liquid it is in
Converging boundaries Oceanic - Continental	The oceanic plate will sink under the continental plate. The continental plate becomes distorted making mountains and volcanoes. where the oceanic plate subducts a trench will from. as the oceanic crust dives down into the hot magma below the continental plate and will meltdown to create more magma
converging boundaries continental - continental	both plates have the same density so neither subduct. instead, the crust crumbles and the plates are both pushed upwards forming mountains
Converging boundaries Oceanic - Oceanic	The plate that is the oldest and most dense will always subduct under the other. This forms a deep trench and a chain of volcanoes called an island arc.
Transform boundaries	Two plates are sliding parallel to each other in opposite directions. the plates often move slowly and then slip past each other, causing an earthquake.
fault lines	fold mountains and many cracks in the rock from Transform boundaries
Divergent plate boundaries continental - continental	a valley forms and sometimes mountains on the outside and streams and rivers in the ridge
divergent plate boundaries Oceanic - Oceanic	seafloor spreading occurs and forms a mid-ocean ridge
Slab Pull	the largest force in plate movement. when two plates collide one is pushed under the other called subduction
Ridge Push	When two plates pull apart, magma from the mantle rises up to fill the gap and forms a raised ridge on the ocean floor. As the ridge is hot and heavy it pushes the rest of the plate away from the ridge, causing it to move.
What is a volcano?	places were extremely hot material from below the earth's surface erupts at the surface
Types of Material that comes out of a volcano	Gases - steam and hydrogen sulphide Ash - fine particles of rock Lava - molten rock Lava bomb
Where do volcanos form	weak spots in the earth's crust and where magma has accumulated below the hot spots Edge of tectonic plate boundaries because the movement of tectonic plates weaken the crust and also generates a lot of heat
Effusive eruption	hot and runny basalt magma reaches the surface
Explosive eruption	when cooler, more viscous magma reaches the surface
Types of volcano eruptions	Explosive, effusive and pyroclastic flow
Pyroclastic flow	where an ash cloud, rock and gas rushes down the volcano like an avalanche
How do volcanoes form at diverging plate boundaries	diverging plate boundaries mostly occur in the ocean therefore most volcanic activity is under the ocean creating new seafloor. Volcanic islands such as Iceland can also occur
Image: Image (binary/octet-stream)	Image: Image (binary/octet-stream)
What volcanoes form at converging plate boundaries	weakness in the crust caused when subduction occurs especially when an oceanic plate subducts it creates a volcano on land because the subducting plate melts and turns into magma and rises to form a volcano and also creates an ocean trench
What is a hot spot	Isolated places where a lot of magma is being created they can occur under both types of crust
What is sonar calculations	The speed of sound in water is 1482m/s Distance (metres) = speed (m/s) x time (seconds) you need to halve the time for the sonar because the sonar will measure how long it will take for the sound to travel there and back
Hotspots on oceanic crust	Creates a chain of volcanic islands - island arc eg) Hawaiian islands
Types of volcanos	Caldera, Shield, Cone and Fissure
what are shield volcanos?	wide and flat volcanoes with gently sloping sides caused by the very runny lava that flows gently and continuously they are formed at hotspots or diverging plate boundaries
What are Cone volcanoes?	built by fragments being ejected from a vent in the shape of a cone with a central crater. They form at subduction zones
What are Fissure volcanoes?	have no central crater, instead, they have giant open cracks in the ground. it expels large quantities of lava that spread really far. when the lava cools and solidifies it stays flat. they do not look like a volcano at all because the cracks are usually buried. usually found at Diverging plate boundaries.
What are caldera volcanos?	the largest and most explosive volcanoes. they usually form under the collapse of land following such a large volcanic eruption. Caldera means cauldron-like.
Classifications of volcanoes	Active, erupting, dormant and extinct
Active Volcanoes?	A volcano that has had an eruption within the last 10,000 years
Erupting volcanoes?	an active volcano that is having an eruption
Dormant volcanoes?	an active volcano that is not erupting but is supposed to again.
Extinct volcanoes?	had not had an eruption for at least 10,000 years and is not expected to again

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