ESS105H1 Lecture Notes - Lecture 1: Metamorphic Rock, Continental Crust, Oceanic Crust

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Published on 30 Jan 2019
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Lecture 1: Earth Science
The Nature of Geology
Geology influences where we live (e.g. Living near volcanic eruptions may seem counterintuitive but ash provides
fertilization for adjacent land)
o Streams: flood hazard, water supply, soil nutrients, etc.
o Too close to mountains = landslides and some slopes are too steep to build on
There is evidence of past global climate change because we can see the change in extent of glaciers and ice sheets
(related to sea levels)
Inside the Earth
The earth is broken up into 3 main layers and these layers are defined by their compositions:
1. Crust: the crust is the highest layer and is split into;
i. Continental crust: thicker & less dense
ii. Oceanic crust: thinner and more dense
2. Mantle: the mantle is the thickest layer and is split into upper and lower mantle
3. Core: the core is the deepest layer and is made of Fe-Ni molten in the outer core and solid inner core
Physical Properties to Consider
The lithosphere consists of the crust and upper mantle while the
asthenosphere is the lower mantle
o The asthenosphere is hot, weak, and mostly solid so it can flow a
little bit
Some regions are higher than others because of the relative thickness of
crust (e.g. Thicker crust will protrude more at top and bottom)
o The relationship between crustal thickness and elevation is called
isostasy
Isostasy if affected by both the thickness and density of the crust
Atmosphere and Earth's Surface
Atmosphere blocks some light and UV, sun's energy converted into IR is also blocked by atmosphere
Land and sea absorb heat
Moreover, different environments form different materials (e.g. Rocks formed in normal surface environments are
sedimentary rocks)
At steep mountain front: Sediment is large, angular, poorly sorted = formed by breaking away from bedrock and
moved downhill under influence of gravity
At sand dunes: Sediment is sand sized and well sorted since sand moved by wind because wind cannot pick up
larger particles
At beach: sediment is rounded
Rock Formation
Igneous rocks: formed from magma
Metamorphic rock: rocks altered by pressure and/or heat
Other rocks formed in hot or deep conditions (e.g.
Precipitation from hot water creates hydrothermal rock)
Weathering: various mechanical and chemical processes
that cause exposed rock to decompose
Erosion and transport: rock/land is worn away through
water, wind, etc. And moved elsewhere
Deposition: where the rock ends up/settles
Uplift: processes involved in mountain building
Burial: covering over of sediment by more and more
layers, leading to compaction and cementation of grains
Deformation: where forces acting on rocks change their
shape through folding, faulting and re-crystallisation
Metamorphism: process of changing rocks (minerals and texture) through heat and/or pressure
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