Oliver Shorttle

Geologist

Michaelmas: the Christmas vacation

Thin Section: Describe the rock and thin section Me3.

— Due for the first supervision of Lent Term, before lectures start —


Essay plans: Go over your notes and read around the subject a bit!
A structured way of doing this is by identifying the 1A tripos questions that relate to the Michaelmas term of the course (which you can access through Moodle), and use these essay titles to construct detailed essay plans. Where you can’t think what you would say, head back to the notes and then onto relevant textbooks to find the information you need and to furnish your answers with more quantitative detail and, especially, real-world examples of the processes you are describing.

Some suggested essays to plan for from the last few years of tripos:

[2019] Describe the observational evidence and theoretical arguments that support the idea that Earth’s mantle is convecting. What methods are available to Earth scientists to estimate the range of temperatures present in the convecting mantle?

[2019] What controls the style of volcanic eruptions? Why are explosive eruptions rare at mid ocean ridges and in rifted environments but common at destructive plate margins?

[2018] Compare the optical properties of minerals that can be observed using a petrographic microscope in plane polarised light with those that can be observed under crossed polars. Explain how optical properties can be used to help identify different minerals. How would we use these properties to distinguish between orthopyroxene and clinopyroxene?

[2017] In what ways do the minerals that make up the Earth’s crust differ from those believed to make up the Earth’s mantle and core? What tools do we have to investigate the likely mineralogy of the deep Earth?

[2015] Describe the observations behind the following apparent paradoxes, and explain how they are reconciled:
a) The inner core transmits S waves but the outer core is liquid
b) The relationship between elevation and crustal thickness on the continents requires the mantle to flow, but it is solid
c) The whole earth transmits P waves and is therefore elastic, but the flexure of the Pacific plate at Hawaii shows that the elastic layer is only about 30 km thick.


Reading: A great book for John Maclennan’s part of the course is Fowler’s Solid Earth, which contains much more than you need to know, but has good clear explanations of key physical processes. The minerals part of the course is nicely expanded upon in Putnis’s Introduction to mineral sciences. For Marian Holness’s part of the course there are a couple of books you might look at, Klein’s Earth Materials and Philpotts’s Principles of Igneous and Metamorphic Petrology are both good; each of which will also contain some examples of real-world occurrences of metamorphic terranes you can use in your essays and photomicrographs to help you relate geological processes to the textures you can see under the microscope. All of these should be in college libraries/UL so you shouldn’t need to buy them.

As a general read, Langmuir’s update of How to Build a Habitable Planet couldn’t be better, but this is a big book so expect reading it to take a while.

After all of this reading you should have plenty of questions for the first supervision next term, so come back with a list of things you want to discuss.

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