Earth’s Interior – Flashcards
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How is Earth's surface changing?
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It's surface has been lifted up, pushed down, bent, and broken
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Why can't geologists dig a whole to the center of the earth?
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The extreme conditions in earths interior prevent exploration far below the surface
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Where and how deep is the deepest mine in the world?
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A gold mine in South Africa, reaches a depth of 3.8 kilometers (that only scratches the surface)
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How have geologists learned about Earth's inner structure?
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Geologists have used two main types of evidence to learn about Earth's interior: direct evidence from rock samples and indirect evidence from seismic waves
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What does drilling into Earth do for geologists?
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It brings up samples of rocks
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What do geologists do with the samples of rocks?
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They can make inferences about conditions deep inside Earth
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What is another way geologists obtain rocks from Earths interior?
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Forces inside Earth sometimes blast rock to the surface from depths of more than 100 kilometers
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What indirect method do geologists rely on to find information about Earth's interior?
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Seismic Waves
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What do earthquakes produce?
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Seismic Waves
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How do geologists study seismic waves?
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They record the seismic waves and study how they travel through Earth. The speed of the seismic waves and the path they take reveal the structure of the planet
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What have scientists learned from seismic waves?
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That earths interior is made up of several layers
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Seismograph
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measures seismic waves
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What are the three main layers of Earth?
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The crust, the mantle, and the core
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What are the characteristics of the crust, mantle, and core?
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These layers vary greatly in size, composition, temperature, and pressure
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What is the rock like just beneath Earth's surface?
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its cool
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When does the rock get warmer?
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about 20 meters down
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What happens 20 meters below the surface?
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For every 40 meters you descend from that point, the temperature rises 1 Celsius degree
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What happens after this rapid rise of temperature?
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it increases more slowly but steadily
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Why are there high temperatures inside Earth?
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They are a result of heat left over from the formation of the planet and also radioactive substances inside Earth release energy
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What is pressure a result of?
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A force pressing on an area
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Why does pressure increase the deeper you travel inside Earth?
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Because the weight of the rock above the pressure increases
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The Crust
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is the layer of rock that forms Earth's outer skin
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Characteristics of Earth's Crust
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The crust is a layer of solid rock that includes both dry land and the ocean floor
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What can you find on the crust?
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rocks and mountains. it also includes the soil and water that cover large parts of Earth's crust
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What is the crust like compared to the layer beneath it?
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Much thinner
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Where is crust thickest?Thinnest?
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under high mountains and thinnest beneath the ocean.
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How thick is the crust, usually?
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5 -40 kilometers thick
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How thick can the crust be?
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up to 70 kilometers thick beneath mountains
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What is the crust called beneath the ocean?
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oceanic crust
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What kind of rock does the ocean floor mostly consist of?
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rocks such as basalt
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Basalt?
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Oceanic rock that is dark with a fine texture
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Continental Crust
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crust that forms the continents
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Which crust consists mostly of granite?
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continental crust
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Granite
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is a rock that usually is a light color and has a coarse texture
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What is about 40 kilometers beneath the surface?
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The Mantle
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What is beneath the crust?
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The solid material of the mantle, a layer of hot rock
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What is Earth's mantle made up of?
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Rock that is very hot, but solid
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How do scientists divide the mantle?
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into layers based on the physical characteristics of those layers
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Overall how thick is the mantle
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3,000 kilometers
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How is the uppermost part of the mantle similar to the crust?
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They are both solid
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Lithosphere?
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The uppermost part of the mantle and the crust together form a rigid layer called the lithosphere
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What does lithos mean in greek?
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stone
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On average how thick is the lithosphere?
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100 kilometers thick
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Why is the part of the mantle just beneath the lithosphere less rigid than the rock above?
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Because it is hotter and under increasing pressure
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Asthenosphere?
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it is soft and can bend like plastic
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What does asthenes mean in greek?
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weak
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The Lower Mantle
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its beneath the asthenosphere and its solid-extends all the way to Earth's core
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What is the core mostly made of?
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Iron and nickel
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What are the two parts of the core?
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The liquid outer core and the solid inner core
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The outer core
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is a layer of molten metal that surrounds the inner core
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Why is it surprising that the outer core is liquid?
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Because of the enormous pressure
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The inner core
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a dense ball of solid metal
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Why is the inner core solid?
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extreme pressure squeezes the atoms of iron and nickel so much that they cannot spread out and become liquid
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What does most of the current evidence suggest about both parts of the core?
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That both contain iron and nickel
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What other substances do scientists think are in the core?
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oxygen, sulfur, and silicon
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What do scientists think liquid in the outer core creates?
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Earth's magnetic field
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What happens when you use a compass?
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the compass needle aligns with the lines of force in Earth's magnetic field
