Earth Science- Continental Drift, Sea Floor Spreading and The layers of The Earth

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Flashcards to study for mid unit test Year 9
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Flashcards by sarah_pryer, updated more than 1 year ago
sarah_pryer
Created by sarah_pryer over 9 years ago
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Question Answer
What are the 4 Layers of the Earth Crust Mantle Outer Core Inner Core
Where are the Asthenosphere and Lithosphere located? Asthenosphere- Below the Lithosphere/ Upper Mantle Lithosphere- Crust and Upper Most Mantle
What is the composition of the Crust? oxygen, silicon, sulfur, oxygen, magnesium and nickel with traces of calcium, aliminuim and other elements.
What is the composition of the lithosphere? Composed of rocks in the crust and the upper mantle
What is the composition of the Asthenosphere? The Asthenosphere conatins most of the mantle.
What is the mantle composed of? Silicate rocks rich in magnesium and iron.
What is the composition of the core? The outer core (liquid) is composed of a alloy of nickel and iron and the same for the inner core but it is solid.
What are the thicknesses of the layers of the Earth? Crust- 30km thick on the continents and 5-10km thick on the oceanic crust. Lithosphere- About 80km thick Asthenosphere- Between 80km to 200km Mantle- 2900km thick Outer Core- 2300km thick Inner Core- 1200km thick
From where does the most understanding of the composition of the Earth and the nature of the Earth's interior come? From Seismic waves that are provided by Earthquakes and from samples taken of thhe Earth's crust.
Rank the following rocks from highest to lowest density and name which layer they come from. Peridotite, Granite, Iron, Basalt 1- Iron (Core) 2- Peridotite (Continental Crust) 3- Basalt (Oceanic Crust) 4- Granite (Continental Crust)
What is density? The degree of compactness of a substances particles
How is density calculated? mass -------------- volume
What happens to the volume of a substance as it is heated? How does this effect its density? The volume increases due to the particles spreading apart which makes the density lower.
How does density relate to the formation of the layers of the Earth? The denser a layer is the lower it will be in the Earth. The core is the densest layer of the Earth therefore it sinks to the bottom because it is the heaviest.
Who was Alfred Wegener? Alfred Wegener was the scientist who proposed the hypothesis (at the time) of continental drift, the hypothesis was never accepted in the scientific community due to lack of explanation until Henry Hess.
What were the four pieces of evidence Wegener found? Matching Coastlines Fossil evidence Climatic Evidence Geological Evidence
Explain further on this evidence Matching coastlines- When the continents were cut out certain continents coastlines matched to others. Fossil Evidence- There was fossils that were the same (species) located on different continents. Climatic Evidence- Coal is only produced in warm climates yet there is coal in England. This indicates that England must of once had a warmer climate/been located closer to the equator. Geological Evidence- There are matching mountain ranges (orogens) on different continents.
Name the smaller supercontinents formed from the splitting of Pangea and describe the continents that made them up Laurasia- Asia, Europe and North America Gondwana Land- Australia, South America, Antarctica and Africa.
Explain the difference between and observation and an inference An observation is something you can use your 'five senses' to determine. An inference is something you assume based on previous knowledge.
Explain the difference between a Hypothesis and a Theory. A hypothesis is an attempt to explain a phenomena when a theory is a widely accepted (in the scientific community) explanation of a phenomena.
Describe the weaknesses in Wegener’s hypothesis and explain the reasons that the scientific community rejected it Wegener did not have an explanation as to how the continents (such big land masses) could be moved. This is why the scientific community rejected his theory.
Who was Harold Hess? Harold Hess was a scientist/marine who discovered the theory of sea floor spreading which was able to explain continental drift. He discovered the mid oceanic ridge aswell.
Describe the observations and evidence used by Harry Hess to explain the unusual topography of the ocean floor in his report: “The history of the ocean basins”. Hess used a magnometer to measure the differnent depths of the ocean floor while he was a marine. From his results he noticed that the ocean floor was not flat and that the ocean floor had different depths. From this he did more research and came up with the theory of Sea Floor Spreading.
What was Hess's evidence? a. Ocean Floor Topography b. Age of Ocean Floors c. Magnetic Patterns. d. Thickness of Sediments e. Location of Earthquakes
Explain on Each Ocean Floor Topography- He used Echo sounding gear to map the sea floor. From this he saw the different depths of the oceans. Age of ocean floors- The closer the sea floor was to the continents the older the sea floor was (Furthest away from the ridge). Magnetic Patterns- The rocks on the ocean floor had different magnetic fields due to when the magnetic field flips. This shows that the rocks were there at different periods in time. Thickness Of Sediment- The older the ocean floor the more sediment that had settled on top.
What is magnetite? Name three iron –rich volcanic rocks that could be found making up the ocean floor. Magnetite is a grey-black magnetic mineral which consists of an oxide of iron and is an important form of iron ore. Basalt Gabbro Dolerite
Explain Sea Floor Spreading Sea Floor spreading is what has happened when an underwater volacano has erupted creating new rock and new sea floor. As the volcano erupts again and again it continues to make more sea floor causing the sea floor to spread.
Describe and explain the process of convection within the mantle and how this relates to plate motion. The convection currents move the plates by the way the current moves (Up, across down)
Explain why there is no oceanic crust that is much older than 200 million years, even though the earth is thought to be 4500 million years old. Due to the subduction of the ocean floor.
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