1.2

• What are the four sections of the Earth's core?

  Inner core: Solid center, mostly iron, hottest at 6000°C. Outer core: Semi-molten, mostly liquid iron and nickel, temperatures between 4500-6000°C. Lower mantle: Solid, but more fluid compared to the upper mantle. Upper mantle: Solid with a semi-molten layer, forming the asthenosphere.
• What is the mantle made up of?

  The mantle is the widest layer of the Earth. The upper mantle is solid, while the lower part is semi-molten, forming the asthenosphere.
• What are the two types of Earth's crust?

  Oceanic crust: Thin and dense (6-10 km), forming the ocean floors.Continental crust: Thicker and less dense (45-50 km), making up landmasses.
• What is the lithosphere?

  The lithosphere is made up of the Earth's crust and the upper mantle, and it is divided into 7 major and many minor tectonic plates.
• How do tectonic plates move?

  Tectonic plates move slowly over the asthenosphere, causing geological events like volcanic eruptions and earthquakes.
• What is mantle convection?

  Mantle convection is a less accepted theory suggesting that heat from radioactive decay in the core heats the lower mantle, causing convection currents in the asthenosphere and driving plate movement.
• What is seafloor spreading?

  Seafloor spreading occurs when hot magma is forced up from the asthenosphere, hardens, and forms new oceanic crust, pushing tectonic plates apart. Paleomagnetism records changes in Earth’s magnetic field in mid-ocean ridges.
• What is subduction?

  Subduction occurs when two tectonic plates move towards each other, and one plate slides into the mantle at a subduction zone.
• What is slab pull?

  Slab pull is a theory suggesting that newly formed oceanic crust at mid-ocean ridges becomes denser as it cools, causing it to sink into the mantle and pull the plate down.
• What happens at divergent (constructive) plate boundaries?

  Plates move apart, forming new crust. This can lead to mid-ocean ridges in oceans or rift valleys on continents. Volcanic eruptions and mild earthquakes are common.
• What occurs at convergent (destructive) plate boundaries?

  Plates move towards each other. Oceanic crust slides beneath continental crust, causing subduction, deep ocean trenches, major earthquakes, and explosive volcanic eruptions. Continental-continental collisions form high fold mountains.
• What happens at conservative (transform) plate boundaries?

  Plates slide past each other. There is no volcanic activity, but powerful earthquakes occur. Plates can stick and release stress, causing shallow-focus earthquakes, such as those in Los Angeles (1994) and San Francisco (1906, 1989).