_07_Plutonism

_07_Plutonism - GEL 1: Lecture 7 Magma and Igneous Rocks:...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
1 GEL 1: Lecture 7 Magma and Igneous Rocks: Up from the Inferno Igneous Rocks An igneous rock forms from the progressive cooling of molten rock (aka crystallization from a melt). It can occur either slowly beneath the surface associated with a magma chamber , or it can occur rapidly on the surface of the land or seafloor as lava ‘freezes’ to rock. (see the Minerals notes on ‘crystallization from a melt’) When magma rises up into the lithosphere, it can do two things: it can erupt on the surface from a volcano or it can solidify at some depth beneath the surface. - igneous rock that solidifies beneath the surface is called intrusive igneous rock and the process is called plutonism . - igneous rock that solidifies on the surface of the land or along the seafloor is called extrusive igneous rock and the process is called volcanism (which we'll discuss separately). The earliest rocks on Earth were igneous. The early Earth was so hot from 'heat of formation' generated by countless collisions with space debris that its surface was likely molten. - as Earth cooled with time, parts of this magma ocean began to solidify into thin crusts (the first 'continents'). As the Earth cooled even more, the entire mantle 'froze', forming a thick, semi-plastic shell around the metallic core. Igneous rocks are the most abundant on Earth, comprising all of the mantle, all of the oceanic crust (remember that all ocean crust forms at mid-ocean ridges), and much of the continental crust. - even though volcanism is a very common phenomenon on Earth's surface, the vast majority of igneous rocks form beneath the surface by plutonism. Where and how is magma produced? Magma forms in the uppermost asthenosphere and throughout the lithosphere and crust where pressures from overlying rock are not as great as deeper in the Earth. - rock in the asthenosphere and deeper mantle is solid. It may be hot and mobile and
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

_07_Plutonism - GEL 1: Lecture 7 Magma and Igneous Rocks:...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online