GEOS1211 Lecture : GEOS1211 Learning Outcomes
14 Jun 2018
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Lecture 3 and 4 learning outcomes
• Appreciate how the Earth formed and its uniqueness
Earth formation->
- ~ 5.5 billion years ago the proto-Earth and other planets condense from gases, dust and plnetismals
- Heating due to friction and compression resulted in a proto-Earth that was largely molten with an outer
crust
- Inner planets- terrestrial, outer planets- gas giants
- After initial accretion of coolish planetismals, proto-Earth rapidly heated up, formed its metallic core within
100 million years
- Molten exterior which quickly cooled to a crust
- After ~4 billion years, the crust begins differentiation into lighter silicic and denser basaltic
-
Eaths uiueess->
- More than half of Earth is covered by water
- Atmosphere is oxygen rich with water vapour clouds
- Diversity of plants and animals
- Goldiloks state- the Earth is at a distance form the Sun such that it receives just enough heat to keep
water from freezing and not so much that it boils
- Enough energy from radioactive decay in the core to fuel the convection cells that keep the plat tectonics
conveyors moving- without these there would be no weathering, erosion of nutrient for soil formation
- Moon causes ocean tides that create intertidal zones from which the first plants and amphibians were able
to colonise continental environments
- Eath is ostl a losed sste ad he thigs happe soehee o the Eaths sufae the effets a
ripple through the whole system
• Compare and contrast physical properties of different planets
Mercury
- Large iron core and a weak magnetic field
- Surface is densely peppered with impact craters and a large multi-ringed basin
- The surface facing the Sun can reach 425 degrees Celsius and the dark side can reach -170 degrees Celsius
- Mercury, Venus and all natural moons are spin orbit coupled
Venus
- Resembles Earth in size and density but lacks a magnetic field
- Slow, retrograde, rotation probably due to drag from the westward-rotating atmosphere which is 90x denser
tha Eaths ad osists of ao dioide, ~.% itoge ad taes of water and sulfuric acid
- Strong greenhouse gas effecr gives the surface a nearly uniform temperature of 460 degrees Celsius
- Surface is monotonous plain with a few massive highlands and evidence of impact craters and basins,
volcanism, chemical weathering and extensive faulting
Mars
- Surface is mainly basalt and dust permeated with permafrost
- Two broad, volcano-tectonic domes bear huge extinct shield volcanoes
- The polar caps consist of seasonal carbon dioxide over permanent water ice and layers of dust and frost
- Chemically the atmosphere of Mars is like Venus but less dense and lacks sulfuric acid
- Martian moons, Phobos and Deimos, are probably captured asteroids
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Jupiter
- Rotational period of 9.84 hrs gives ~7% flattening
- Silicate & Iron & water core enclosed by lower mantle of metallic hydrogen and upper mantle of liquid
hydrogen
- Atmosphere is mainly hydrogen and helium
- Minor carbon dioxide, methane and ammonia
- Winds blow parallel with the equator at ~150m/s in dense bands flowing in alternate directions
- Great Red Spot is a huge stationary storm
Saturn
- Resembles Jupiter but smaller, less dense, flattened and more prominent rings
- “i of “atus atual oos ae sall, of lo desit ad ae ateed
- Titan has a nitrogen atmosphere and possibly methane clouds, rain and ocean
- Jupiter and Saturn have several small asteroidal moons
Uranus and Neptune
- Uranus and Neptune are smaller and denser than Jupiter and Saturn
- Atmospheres are richer in methane, ammonia and water
- Uauss fie sall oos ad eptues oe lage moon are rock/Iron mixtures
- Neptune erupts liquid nitrogen and soot
Pluto (dwarf planet)
- Pluto is smaller and less dense than Earth
- It has an eccentric inclined orbit that lies inside that of Neptune at perihelion
- It could be an asteroid or an escaped moon of Neptune
• Summarise and explain the main differences in the chemical composition of the solar system, the Earth as
a whole, and Earth’s crust
Solar system->
- Hydrogen, Helium, Neon, Silicon, Argon, Iron,
- Universe-> 76% Hydrogen, 23% Helium, 1% rest
- Hydrogen, Heliusm, Carbon, oxygen neon, Silicon, Sulfur, Argon, Iron Nickel
Earth->
- 90% Iron, Oxygen, Silicon, Magnesium
- Mantle-> oxygen, magnesium, silicon, calcium, titanium, chromium, iron, nickel, barium-lead
Eaths ust->
- rock forming elements, rare earth elements
- Hydrogen carbon, oxygen, silicon, potassium, calcium, titanium, iron, strontium, zirconium, barium, lead
- Oxygen 46.6%, Silicon 27.7%, Aluminium 8.1%, Iron 5%, Calcium 3.6%, Sodium 2.8%, Potassium 2.6%,
Magnesium 2.1%, Titanium 0.4%, Hydrogen 0.1% (these are the 8 most common elements in the Crust)
• Describe plate tectonic boundary types and common geological features, with examples
Topography, heat flow, earthquakes, volcanoes occur at plate boundaries. Mountain ranges, deep trenches, gigantic
mid-ocean ridges very old crust, very young crust. Back-arc basins, fault and fold mountain ranges, volcanic island
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arcs, volcanic island chains, abyssal plains, seamounts. Geometric and geological fit. Flora and fauna. Glacial
sediments.
Continental drift-
- Expanding earth model, but problems- 1. Why would the earth expand and 2. How do major mountain ranes
form?
- Model of 1920s- Wegner, Holme, but problems- 1. How can continents plow through oceans and 2. How
does the conveyor belt operate?
A new theory is required (this was the theory of plate tectonics). Permits:
1. Continents to drift
2. Creation of new crust
3. Destruction of old crust
4. Retention of old continental crust
5. Physics to work
Continental drifting- how do we know?
- Creation of new oceanic crust
o Mid-atlantic ridge
- ‘ealised oea sediets ee thi ad ust ee ugged ad e, deeloped theo of oea-floor
speadig
- Frederick Vine and Drummond Mathews showed how the magnetic stripes were due to a combination of
magnetic reversals and the creation of new ocean crust
- Magnetic striping and polarity reversal
o Spreading-ridges and magnetic anomalies
- Creation of new oceanic crust
- Spreading ridges and magnetic anomalies
- Ocean ridges, hot springs, sulphides, exotic life forms
- Mid-oceanic hotspots and volcanic island chains
- Distribution and age of Hawaiian volcanoes
- Destruction of old (oceanic) crust- subduction
o Evidence- 1. Speed of seismic waves, 2. Heat diffusion at surface, 3. Topography (trenches), 4.
Earthquake foci, 5. Volcanoes
- The Indonesian Arc
- Various subduction styles-
o ocean-continent (Peru-Chile trench- Nazca plate under South American plate)
o ocean-ocean (Japan trench- pacific plate under Eurasian plate)
o continent-continent (Himalayan collision zone- Indian-Australian plate under Eurasian plate)
- Transform faults occur where plates are sliding past one another or within plates to accommodate different
rates of motion
- Styles of boundaries and earthquakes-
o Divergent boundary-
o Transform fault boundary
o Continental collision boundary
o Subduction zone boundary
• Relate tectonic processes to landforms and seismic and volcanic processes
Lecture 5 learning outcomes
• Define what is a mineral
- Naturally occurring
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