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Science: Key Concepts


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What happens at deep-ocean trenches?
In a process taking 10s of millions of years, part of the ocean floor sinks back into the deep-ocean trenches
What causes convection currents?
Heating and cooling of the fluid, changes in the fluid's density, and the force of gravity combine to set convection currents in motion
What was Alfred Wegener's hypothesis about continents?
Wegener's hypothesis was that all the continents had once been joined together in a single landmass and have since drifted apart
What are the 3 types of plate boundaries?
There afe 3 kinds of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaris. A different type of plate movement occurs along each.
What is the process of sea-floor spreading?
In sea-floor spreading the sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added. As a result, the ocean floors move like conveyor belts, carring the continents along with them.
How have geologists learned about Earth's inner structure?
Geologists have used 2 main types of evidence to learn about Earth's interior: direct evidence from rock samples and indirect evidence from seismic waves
What is the theory of plate tectonics?
The theory of plate tectonics explains the formation, movement, and subduction of Earth's plates
What evidence supported Wegener's hypothesis?
Wegener gathered evidence from different scientific fields to support his ideas about continental drift. He studied land features, fossils, and evidence of climate change
How is heat transferred?
There are 3 types of heat transfer; radiation, conduction, and convection
Why was Wegener's hypothesis rejected by most scientists of his day?
Wegener could not provide a satisfactory explanation for the force that pushes or pulls the continents
What is the evidence for sea-floor spreading?
Several types of evidence supported Hess's theory of sea-floor spreading eruptians of molten material, magnetic stripes in the rock of the ocean floor, and the ages of the rocks
What causes convection currents in Earth's mantle?
Heat from the core and the mantle itself causes convection currents in the mantle
What are the characteristics of Earth's crust, mantle, and core?
The 3 main layers of Earth are the crust, the mantle, and the core. These layers vary greatly in size, composition, temperature, and pressure

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