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Lecture 6

EESA06 Lecture 6 Notes

Environmental Science
Course Code
Nick Eyles

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Lecture 6
During the hydeian period: first time period of earth it was known as
the period of hell
Rocks were molten, no life could exist, no ocean or atmosphere
Things changed, planet differentiated: heavy elements such as iron and
magnesium were able to sink, at first it was homogenous and then sank to
the center of the earth resulting in the core
Once that happened when we have the core, mantle and the crust, we were
able to get to the conditions for life to being on planet earth
Once planet has been differentiated, there were a magnetic field, holding all
the gases escaping from the hot magma of the mantle resulting in building an
atmosphere and oceans
There are four major steps
How they are formed: a cavity is filled in with minerals such as calcium
carbonate and silica or iron. Taking what was an empty space and taking
water and circulating water and pulls minerals and precipitate in the shell
SLIDE1: Picture of stumps: Petrified forest in Arizona; fossilized stumps,
minerals have came in and precipitated
Process is called permineralization: sedimentation is when sediments
pile up on the creature. Colour of the fossil doesnt have anything to deal with
the colour of the creature, it is the chemical of the rock
As more sediments pile up, there are more pressure and lithication: turning
something into a rock. The bottom rocks get crushed and eventually become
lithified and become a sedimentary rock
In mineral rich water some of the mineral are able to precipitate out of the
water and fills in the cavities of the creatures.
Plate tectonics give uplift or two continental crust thickens that build
himylias crumples rocks and pushes them to a higher level
Can be due to erosion that ware away the rocks
No plate tectonics will result in the whole world being ocean because of no
mountains and simply just erosions
Ammolite(gemstone) have identical halves Ammonite(fossil)

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Almost all fossils are found in sedimentary rocks except Mount Vesuvius
Pompeii fossilized people due to pyroclastic flow. Buried from ash
Trace fossils/ichnology: your pathways were preserved NOT you died there
e.g. plant roots
Creatures that hide under the sand look for protection against predators or
looking for food
Bioturbation: mixing of life, life ruining sediment columns
Crinoid: Slide 6, sea lily: mobile but not tough when storms came they are
busted. Broken stems and rings that pile up. Rocks of southern Ontario
Reason for Palaeoecology: want to study the evolution of life, or how
different organisms live in relation to the environment, they want to know
what the environment was like on earth before humans
Fossil morphology: the way its shaped, hard/soft
Assemblages: group of fossils that are found together because they
live in similar environment. Strong indicator of type of environment
Stratigraphy: layers of rock, piecing together earth before humans
Geologists are good descriptive but not good at explaining
Fossils enabled to say relative ages
William smith: digging canals noticing fossils are in the same order
principle of faunal succession: geological range in time; first and last time a
species appeared
Geological time scaled originally did not have time SLIDE 8 it would indicate
a certain rock was from a certain period but not how long ago
Most useful fossils are short lived but not those that are from uncommon
places, so widespread is important index fossils e.g. ammolite
Shorter lines are here for briefer times SLIDE 9
Earliest single-celled organisms
Most of earths history was in the Precambrian time
Slide 11, this scale is distorted because only the top few centimetres will be
reprehensive, they shorten the Cambrian
3.8 billion years old formation of life. 4.56 bya
No magnetic field, a lot of meteorites hitting earth
Sir James Dawson: decision of the oldest fossil 1858) Eozoon Canadense
The dawn animal of Canada: now
recognised as mineral not organic
NOT fossil
It is called the dubio fossil
Prokaryotes: earliest bacteria
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