Week 1 Flashcards
What are the three types of rock?
1- Igneus
2- Sedimentary
3- Metamorphic
Remember the age of the earth
4.5 billion years ago
How were igneus rock created?
They were created by geological processes involving extreme heat
What are the two types of igneus rock?
Extrusive and Intrusive
Example of extrusive igneus rock
Basalt
Example of intrusive igneus rock
Granite
Extrusive cools ____?
Quickly
Intrusive cools___?
Slowly
Which type of igneus rock come from magma?
Intrusive
Which type of igneus rock come from lava?
Extrusive
Large crystals can be found in ____?
Intrusive rocks
How were sedimentary rocks formed?
By sedimentation
Which are the two types of sedimentary rocks?
Fragmental, Biogenic
Describe fragmental sedimentary rock and one example
Small bits of the rocks (limestone)
Desrcibe biogenic sedimentary rock and give one example
It contains materials from previously living organisms (Coal)
Where can you find fossils?
In sedimentary rock formations
Desrcibe metamorphic rocks and give one example
Pre-existing rocks have been compressed and shaped and for this reason it became a different rock (Schist)
Which are the two methods for dating rock?
Relative Dating and absolute dating
Describe relative dating
Fossils help us dating the rock because it means that when the organism was around the rock formed (but it can also be compared to other rocks)
Absolute dating:
Based upon the decay of radioactive substances
From which type of rock comes the most reliable dates and why?
They come from igneus rock because they crystallize quickly compared to sedimentary rocks
When did the big bang took place?
14 billion years ago
What’s the age of the oldest rocks on our planet?
3.8 billion years ago
When was our galaxy formed?
In the first few billion years after the big bang
What’s the name of the process by which Earth was formed?
Planetesimal Accretion
What’s planetesimal accretion?
Small pieces of rock collapsed together forming bigger rocks and then a planet.
How was our planet initially?
It was mostly silicon, iron and magnesium with smaller amounts of natural chemical elements
Initially the planetesimals were cold, but after coming together they started heating up for three main reasons, tell them.
- Impact
- Pressure
- Radioactive Disintegration
What’s radioactive disintegration (decay)
Radioactive elements are unstable and the always try to move to a more stable state and they do this by giving off radiation. Every radioactive istope decay at its own fixed rate.
What are the source of modern Earth heating?
- External: nuclear fusion of the Sun provides energy to the atmosphere and ocean driving climates and weather
- Internal: the legacy of the origin of our planet (differentiation, radioactive decay, core providing heat) and it drive plate tectonics.
What’s the Iron Event
As Fe melted large drops of it formed and they fell toward the centre of the planet, displacing lighter material which floated on the top.
1-This lead to the formation of a liquid core
2- The formation of a liquid core created a gravitational energy converted into heat.
3- The Heat generated produced temperature of 2000 degrees causing a large part of the planet to melt.
This process converted the Earth from an homogeneus body into a shelled body with a dense iron core and a crust and between them the mantle.
When did Oxygen appeared in the atmosphere?
2.4 Ga as a result of the appearence of photosynthetic algae (So it’s a consequence of life)
Describe the core:
The outer core is liquid while the inner is either solid and liquid (highly viscous). It’s composed of a Fe-Ni mixture.
(3500 km)
Describe the mantle:
It’s the layer between the top of the core and the base of the crust. Solid but it behaves as a viscous fluid.
(3000 km)
Desrcibe the crust:
Outermost layer and makes <1% of the total volume of the planet. It includes both oceanic and continental crust.
(5-40 km)
Describe continental crust:
It’s mostly granitic formed by vulcanic activity exposed to the air. High in Silicon and Alluminium (SiAl). (25-40 km)
Describe oceanic crust:
A little more denser than the continental crust. Basaltic composition because when you get lava erupting from the mantle ecounters cold water it cools quickly. High in silicon and Magnesium (SiMa). (5 km)
Describe the litosphere:
Rigid, brittle outer layer of the Earth composed by the crust and the upper part of the mantle (80-150 km).
Describe the astenosphere:
Part of the upper mantle directly below the astenosphere. It’s a weak plastic part beacuse 5% of it it’s melted.
What’s isostasy?
Condition of gravitational balance that is attained by Earth materials of differing densities, comparable to floating, that exists between the continental crust (sial) and the underlying oceanic crust (sima)
Explain the distribution of volcanic and seismic activity on modern earth
These activities are restricted to well-defined belts located at the edge of important tectonic plates. Beacuse these areas form the basis for the sub-division of the brittle litosphere into a number of rigid plates.
What’s plate tectonics?
Is the movement of tectonic plates on the litoshpere driven by convective circulations in the underlying astenosphere.
Why does the astenosphere moves?
Because it’s partly liquid and this motion propels the litosphere above it.
What are the three types of motion possible for tectonci plates?
1- Divergence
2- Convergence
3- Lateral Motion
Describe divergence motion:
Occurs at costructive plate margins where oceanic litosphere is created by magma coming up from the mantle.
Give an example of costrusctive plate margin:
Mid-Atlantic Ridge
Describe convergence motion:
Occurs at destructive plate margins, where one fo the two plates become destroyed in the process. Dense oceanic litosphere is being subducted beneath less dense continental litosphere. At the subductive zones the friction generates magma and this form vulcanoes and mountains.
Give an example of destructive plate margin:
West coast of South-America
Desrcibe lateral motions:
Occurs at conservative plates margins where litosphere is neither destroyed or created.
What are the consequence of tectonic movements for biological sciences?
That continents were one attached forming Pangea (225 million years ago) and then they separated so this modified the distribution of plant and animals. But also that geographical siolation can lead to speciation.
