Intraplate Volcanism Flashcards
Explain the formation of volcanoes which is associated with mantle plumes rather than inter-plate boundaries
Active volcanoes can be formed in the middle of tectonic plates, above hotspots (a large reservoir of heat in the mantle caused by plumes of magma rising to the asthenosphere). When the magma plumes burn through structurally thin or weak parts of the lithospheric crust, it escapes onto the seabed. The layers harden and build up over time until volcanic islands have been created. A chain of islands is created over millions of years as tectonic plate movement results in the island being dragged away from the hotspot. An example is The Emperor Sea Mount Chain. The active volcanoes above the mantle plume are called shield volcanoes. These erupt low viscosity magma, frequently, which spreads a vast distance resulting in gently sloping, dome shaped volcanoes.
Define lithosphere:
The lithosphere is the solid, outer part of Earth, including the brittle upper portion of the mantle and the crust.
Define asthenosphere:
zone of Earth’s mantle lying beneath the lithosphere and believed to be much hotter and more fluid than the lithosphere.
Who was Alfred Wegener and what did he say?
Alfred Wegener was a German meteorologist who first presented the concept of the supercontinent, Pangea. He also put forward the first comprehensive theory of continental drift.He suggested biological, climatological and geological evidence to back his theory, but he could not prove HOW his theory worked.
Give some Biological evidence to back up Alfred Wegener:
- Wegener also compiled evidence by comparing similar rocks, mountains, fossils, and glacial formations across oceans. For example, the fossils of the primitive aquatic reptile Mesosaurus were found on the separate coastlines of Africa and South America. He pointed out these were land-dwelling creatures that could not have swum across an entire ocean.
Give some Geological evidence to back up Alfred Wegener:
- Wegener’s first piece of evidence was that the coastlines of some continents fit together like pieces of a jigsaw puzzle. People noticed the similarities in the coastlines of South America and Africa on the first world maps, and some suggested the continents had been ripped apart
Give some climatological evidence to back up Alfred Wegener:
Mountains containing impressive glacial landforms is puzzling evidence that glaciers once existed in normally very warm areas in southern Africa, India, Australia, and Arabia
What is Sea floor spreading and how does it prove Wegener’s theory?
Sea Floor Spreading occurs when two oceanic plates move away from each other, allowing magma from the mantle to rise and form new crust ridges within the ocean, resulting in a successively younger and wider ocean floor. This flow of material is thought to bring about the migration, or drifting apart, of the continents.
What is Paleomagnetism and how does it prove Wegener’s theory?
Paleomagnetism is the study of magnetic fields frozen within rocks. In their liquid state as magma or lava, the magnetic poles of the minerals align themselves with the Earth’s magnetic field. When the rock cools and solidifies, this alignment is frozen into place. these magnetic reversal patterns can be used to support the model for seafloor spreading, where new crustal material pushes old crustal material away from the ridge.
What are earthquake P, S and L waves, and what effect do each of them have?
-P waves: primary waves, they push and pull the rock. They don’t cause any shaking - just weaken the rock as they pass through it.
-S waves: secondary waves, they pull the rock up and down. Slower - but do cause ground shaking.
-L waves: Surface waves, they move the rock side to side. They cause the highest rate of ground shaking.
Earthquake waves cause crustal fracturing, groundshaking and secondary hazards.
What are the primary hazards associated with earthquakes?
- ## The only primary hazard of earthquakes is groundshaking. The severity of the groundshaking can have a major impact on possible secondary hazards. For example, the Haiti earthquake in 2010 had a magnitude of 7.0 on the Richter.
What are the secondary hazards associated with earthquakes?
