Earth

• What is the mantle of the Earth?

  The mantle is a thick layer of dense, semi-liquid rock extending about 2900 km below the Earth's crust.
• What is a discontinuity in geological terms?

  A discontinuity is the place where one Earth layer stops and another begins.
• What is the Mohorovicic Discontinuity commonly referred to as?

  The Mohorovicic Discontinuity is commonly referred to as the Moho Discontinuity.
• Why do seismic waves change velocity at a discontinuity?

  Seismic waves change velocity due to the greater density of the mantle and the lesser density of the crust.
• What are the tectonic plates mentioned in the study material?

  • North American Plate
  • Nazca Plate
  • African Plate
  • Indo-Australian Plate
  • Antarctic Plate
  • South American Plate
  • Eurasian Plate
  • Pacific Plate
• How did the theory of plate tectonics change ideas about the structure of the Earth?

  The theory of plate tectonics paved the way for the discovery and classification of new zones and structures.
• What are the four main structural layers of the Earth?

  • Crust
  • Mantle
  • Outer Core
  • Inner Core
• What are the spheres into which the Earth is divided?

  • Atmosphere
  • Lithosphere
  • Asthenosphere
  • Mesosphere
• What is the asthenosphere?

  The asthenosphere is a zone of the Earth's mantle beneath the lithosphere consisting of several hundred kilometers of deformable rock.
• What evidence supports the Theory of Plate Tectonics?

  • Jigsaw pieces of continents
  • Matching fossils
  • Glacial evidence
  • Magnetic striping
  • Modern observations
  • Matching rock types/layers
• What does the Theory of Plate Tectonics state about the Earth's lithosphere?

  The Theory of Plate Tectonics states that the Earth's lithosphere is divided into a number of plates that move relative to each other.
• How fast do tectonic plates move on average?

  Tectonic plates move on average 20 cm a year.
• What accounts for the distribution of earthquakes, volcanoes, and mountain belts?

  The interaction of tectonic plates along their contact boundaries accounts for the distribution of earthquakes, volcanoes, and mountain belts.
• What are convergent or collision boundaries?

  Convergent or collision boundaries are where one plate collides with another, leading to subduction zones.
• What happens at a subduction zone?

  At a subduction zone, one plate slides underneath another and moves down into the mantle, leading to destructive processes.
• What is the main driving force of plate tectonics?

  The main driving force of plate tectonics is gravity.
• What is subduction?

  Subduction is the process where dense oceanic lithosphere dives beneath another plate and sinks into the mantle.
• How does oceanic lithosphere affect plate motion?

  The sinking oceanic lithosphere drags the rest of the tectonic plate, which is the main cause of plate motion.
• What creates mid-ocean ridges?

  The process of oceanic lithosphere being pulled apart in several directions creates mid-ocean ridges.
• What causes convection currents in the mantle?

  Convection currents in the mantle are caused by heat from deep within the Earth causing molten rock to move upwards and cool rocks to sink.
• What happens when hot mantle rock comes into contact with the cold crust?

  When hot mantle rock comes into contact with the cold crust, it cools and sinks.
• What are the key processes involved in plate tectonics?

  • Movement of tectonic plates
  • Subduction and recycling of rock
  • Creation of mid-ocean ridges
  • Interaction at plate boundaries
  • Convection currents in the mantle
• What are the four main layers of the Earth?

  Crust, Mantle, Outer Core, Inner Core
• What is the theory of Plate Tectonics?

  It states that the Earth is made up of rock plates that rest on the mantle and move over geological time.
• Why was Wegener’s theory on Continental Drift initially not accepted?

  There was no plausible mechanism to support his theory at the time.
• How did Plate Tectonics contribute to the acceptance of Continental Drift?

  It provided the mechanism for the movement of continents, leading to its acceptance in the 1960s.
• What is a scientific theory?

  An explanation for a set of observed facts supported by a large body of evidence.
• What type of evidence supports the Theory of Plate Tectonics?

  Jigsaw pieces, matching fossils, glacial evidence, magnetic striping, modern observations, and matching rock types/layers.
• What evidence suggests that continents were once joined?

  • Jigsaw pieces fitting together to form Pangea
  • Matching fossils across continents
  • Glacial evidence showing ancient glaciers
  • Magnetic striping indicating continental movement
  • Matching rock types and layers
• What does the jigsaw piece evidence indicate about the continents?

  It shows that continents were once part of a single land mass called Pangea.
• How does the composition of rocks relate to their formation environment?

  The composition is determined by the location and environment in which the rock is formed.
• What similarities exist between the mountains of Northern America and north-western Europe?

  The structure and rock composition of these mountains can be matched, indicating they were once joined.
• What evidence do matching rock layers provide?

  They indicate that different continents were once connected and have since separated.
• What are some examples of matching fossils found on different continents?

  Glossopteris and Lystrosaurus.
• What is tillite and how is it formed?

  Tillite is a sedimentary rock formed from debris left by glaciers.
• What evidence do ancient glaciers provide regarding continental movement?

  They show that continents have moved from colder climates to their current locations.
• What is the significance of the magnetic rocks found in North and South America?

  They show that the continents have shifted, as their magnetic poles point in different directions.
• How does sonar work?

  Sonar uses low-frequency sound waves to bounce off objects and interpret the echo.
• What did military sonar technology reveal about the ocean floor rocks?

  The ages of the rocks range from brand new to 200 million years old.
• What do the parallel magnetic stripes on the ocean floor indicate?

  They indicate the reversal of the Earth's magnetic field and the age of the rocks.