Introduction 1-3 Flashcards
Continental Rock average denisity
2.7 tonnes/m3
Earth Density
5.52 tonnes/m3
Iron density
13 tonnes/m3
Depth of Core
2890km
Types of body waves (2)
P - Primary/Compressional
S- Secondary/Shearing
What Type of earthquake wave cannot pass through liquids?
S-Waves
Composition and State of Outer Core
90% Iron-Nickel
10% Light material
Liquid
Name of Boundary between Crust and mantle
Mohorovicic Discontinuity
Depth of Mantle
25-90km below Continental
6-11km below Oceanic
How do plates move if the mantle is solid
Solid state convection
What is Isostasy?
Crust floating in equilibrium above the mantle
state of gravitational equilibrium between Earth’s crust and mantle such that the crust “floats” at an elevation that depends on its thickness and density. This concept is invoked to explain how different topographic heights can exist at Earth’s surface
Describe crust compositions (Rock-type, Density, Material)
Continental: Granitic, 2.7g/cm3, Silica-rich
Oceanic: Basaltic, 3g/cm3, less but still Silica-rich with more iron, magnesium and calcium
Mantle composition
Peridotite, 3.3g/cm3, High in Magnesium and Silica
Depth of inner core
5155 km
What is the Asthenosphere
- Region of the upper mantle
- Below the lithosphere, 80 and 200 km depth
- Slowly solid-state connects
- Mechanically weak and ductile
What is the lithosphere
- Rocky outer part of the Earth
- Made up of the brittle crust and the top part of the upper mantle
- Coolest and most rigid part of the Earth
3Cs and 3 Ps of planetary formation
Coalescence - Coming together into a dark then solar nebula
Condensation - Into solid grains
Coagulation - of Atoms into larger particles
Planetesimals - 100,000 years later into 10km blocks
Planetary Embryos - 50,000 years later into 1000km blocks
Planets
What is the earthquake cause called?
Stick slip
Types of surface waves
Rayleigh Waves - rolling
Love Waves - side to side
Earthquake scale 2 types and examples
Magnitude - Richter
Intensity - Mercalli
Ophiolites are?
- Pieces of oceanic crust
- Escaped subduction
- Preserved on land
What is Decompression melting?
- Melting while rock stays at the same temperature
- Pressure Reduced causes melting
- Due to rock being moved toward the surface
What is Partial melting?
- Melting where only part of the rock is melted
- As the rock has minerals with different melting points these melt preferentially
- This makes the melt have a different composition to the solid
What is Mafic rock?
- Rock rich in magnesium and iron (typically igneous)
- Dark in colour
- Common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite
- Common mafic rocks include basalt, diabase and gabbro.
What is orogeny?
- Mountain forming event on continents
- Plate margin is crumpled and uplifted against another continental plate
4 types of plate margins
Convergent/Subduction/Destructive
Divergent/Constructive
Transform/Conservative
Collision
6 Paleozoic Periods from oldest to newest
Cambrian Ordovician Silurian Devonian Carboniferous Permian
Campers Order Silver Devils to Carry Persons
5 lines of evidence for Continental drift
1) Matching Geology and Orogenic Events on both sides of the Atlantic
2) Matching fossils across the Atlantic e.g. Fresh Water Mosasaurus’ in both Africa and South America indicating a freshwater sea/lake on them both
3) Carboniferous coal deposits linked across the Atlantic
4) Glacial evidence in Oman and Peru from an Antarctic source
5) Paleomagnetic Data e.g. Paleolatitudes
Evidence for Plate Tectonics (3)
1) Global Distribution of volcanoes and Earthquakes
2) Wadati-Benioff zones - Subduction processes of a plate passing under; Earthquakes caused by cold material at 200km deep
3) Magnetic reversals recorded in the oceanic crust: Radiometrically dated seafloor had crystallised according to the magnetic field when the crust cooled past it’s Curie Point.
Phanerozoic eon
Visible life; Our eon we are in now
Precambrian
SuperEon Before the Cambrian period; the earliest Eon in Earth’s history
3 Eons of the Precambrian
Proterozoic - Early life; started with free oxygen formation (Great Oxygenation Event); development of eukaryotes; CO2 removed by plate tectonics recycling carbon-rich sediments into the mantle and the growth of oceans for CO2 to be dissolved in seawater
Archean - Start of plate tectonics and first life and fossils in the form of stromatolites; microbial mats of cyanobacteria;
Hadean - First eon, fiery hell, oldest remaining rocks
