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Earth structure and global tectonics

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What is the Earth made of inside, and how do seismic waves prove it?

Earth structure: the layered internal structure of the Earth (crust, mantle, outer core and inner core) and the mechanical layers (lithosphere and asthenosphere); the seismic evidence for the layering from changes in P and S wave velocity at boundaries such as the Moho; the P and S wave shadow zones as evidence for a liquid outer core; the use of meteorites and density as evidence for the composition of the core and mantle.
A focused answer to the Eduqas Geology statement on Earth structure. Covers the crust, mantle, outer and inner core, the lithosphere and asthenosphere, the seismic evidence from P and S wave velocity changes and the Moho, the shadow zones proving a liquid outer core, the meteorite analogy for the core, and locating an earthquake epicentre from the P-S travel-time gap.
14 min answer →

How are earthquakes generated and measured, and how do we locate the epicentre?

Earthquakes and seismic waves: the focus and epicentre; the elastic rebound mechanism; the P, S and surface waves and their properties; the difference between magnitude (the logarithmic Richter scale and its saturation, and the moment magnitude scale) and intensity (the Modified Mercalli scale); the use of P and S wave arrival times and travel-time graphs to locate an epicentre by triangulation.
A focused answer to the Eduqas Geology statement on earthquakes. Covers the focus and epicentre, the elastic rebound mechanism, P, S and surface waves and their properties, the difference between magnitude (Richter saturation and moment magnitude) and intensity (Modified Mercalli), a worked example using the P-S travel-time gap, and how triangulation from three stations locates an epicentre.
14 min answer →

What happens at the three kinds of plate margin, and what features identify each?

Plate margins and their features: the processes and characteristic features of constructive (divergent), destructive (convergent) and conservative (transform) margins; the sub-types of destructive margin (ocean-ocean island arcs, ocean-continent margins and continent-continent collision); the Benioff zone, subduction and decompression melting; the diagnostic rocks, structures, earthquakes and volcanoes of each margin type.
A focused answer to the Eduqas Geology statement on plate margins. Covers constructive (divergent), destructive (convergent) and conservative (transform) margins, the ocean-ocean, ocean-continent and continent-continent sub-types, the Benioff zone, subduction and decompression melting, and the diagnostic rocks, structures, earthquakes and volcanoes that identify each margin in the exam.
14 min answer →

What evidence built the theory of plate tectonics, and what keeps the plates moving?

Plate tectonics theory and evidence: the development of the theory from Wegener's continental drift, through Hess's sea-floor spreading, to plate tectonics; the evidence of palaeomagnetism and the symmetrical magnetic striping of the ocean floor; the increasing age of oceanic crust away from mid-ocean ridges; the driving mechanisms of mantle convection, ridge push and slab pull.
A focused answer to the Eduqas Geology statement on the development of plate tectonics. Covers Wegener's continental drift evidence and why it was rejected, Hess's sea-floor spreading, palaeomagnetism and symmetrical magnetic striping, the increasing age of oceanic crust away from ridges, a worked spreading-rate calculation, and the driving forces of mantle convection, ridge push and slab pull.
14 min answer →

How do the lithosphere, isostasy and mantle plumes shape the Earth away from plate margins?

The lithosphere, mantle plumes and hotspots: the structure and composition of oceanic and continental lithosphere; the principle of isostasy and isostatic adjustment; mantle plumes and hotspots as a cause of intraplate volcanism; hotspot tracks and the age progression of volcanic island chains (for example Hawaii); the basis of the Component 3 geology of the lithosphere option.
A focused answer to the Eduqas Geology statement on the lithosphere, mantle plumes and hotspots. Covers oceanic and continental lithosphere, the principle of isostasy and isostatic rebound, a worked density calculation, mantle plumes and hotspots as a cause of intraplate volcanism, hotspot tracks and the age progression of island chains such as Hawaii, and the Component 3 lithosphere option.
14 min answer →

What controls how a volcano erupts, and what products and landforms result?

Volcanic activity and eruption styles: the control of silica content, viscosity and dissolved gas on eruption style; the contrast between basaltic effusive eruptions (shield volcanoes and fissures) and andesitic or rhyolitic explosive eruptions (stratovolcanoes, pyroclastic flows and calderas); the volcanic products (lava, tephra and pyroclastic material); the link between eruption style and plate setting.
A focused answer to the Eduqas Geology statement on volcanic activity. Covers how silica content, viscosity and dissolved gas control eruption style, the contrast between basaltic effusive and andesitic or rhyolitic explosive eruptions, the products (lava, tephra and pyroclastic material), the landforms (shield, stratovolcano, caldera and fissure), and the link to plate setting.
13 min answer →