CHAPTER 2.1 Earth's Geological Beginnings Flashcards
Early Earth Conditions
- Atmosphere —
- Meteor and comet strikes were common
- Moon was much closer
- There was —
- Very little —
lacked free oxygen
more volcanic activity
land
Earth’s Sphere
biosphere -
geosphere - terrestrial
hydrosphere - water
atmosphere - gaseous layer above
cryosphere -
the realm of life
ice frozen
Layers of the Earth
definition
1. Chemical Layering -
2. Physical/ Mechanical Layering -
- based on composition
- based on rigidity
Chemical Layering
Basic Composition - rocky, metallic
what are the layers according to chemical layering and what are they composed of?
crust - composed of Silicates
mantle - composed of Silicates
core - composed or Iron
Physical layering
what are the layers of the earth according to physical layering?
a. lithosphere - rigid outer layer (crust)
b. astenosphere - solid rock that flows slowly (plastic)
c. mesosphere - middle layer and solid part of the lower mantle
d. outer core - liquid (Fe, Ni layer)
e. inner core - solid (Fe, Ni; very dense)
type of crust
very dense, made of basalt, thin and young (5-7 km)
chemical layering
oceanic crust
type of crust
less dense, made of granite (10-70 km)
chemical layering
continental crust
- composed of Mg, Fe and Si
- layers are heterogenous
- more solid near the surface
- contains Astenosphere (plastic layer)
chemical layering
mantle
- composed of Ni and Fe
- very hot and is 1/3 of earth’s weight
chemical layering
core
Discontinuities on the layers of Earth
- boundary between crust and mantle
- boundary between mantle and outer core
- boundary between outer core and inner core
Mohorovicic discontinuity
Gutenberg discontinuity
Wiechert discontinuity
Evidence that Earth is Layered
S-waves - does not travel on liquids, travels on plastic but slow causing angle of deflection (travels on solid - discovery of core)
P-waves - travels any type of medium (primary wave, first wave - earthquake)
due to S and P waves
Who proposes Continental Drift Theory?
Alfred Wegener
one ocean
panthalassa
Evidences for Continental Drift
Matching coastlines
South America and middle of Africa
North America and north of Africa
Greenland and Europe
Asia and Australia
Evidences for Continental Drift
Matching fossils
Cynognathus (triassic land reptile) - S. America and Africa
Lystrosaurus (triassic land reptile) - Africa, India, and Antartica
Mesosaurus (freshwater reptile) - S. America and Africa
Glossopteris (large Pteridophyte) - all of the southern continents
Evidences for Continental Drift
Matching Glacial Deposits
all Southern areas S. America, Africa, India, Australia, and Antartica
as the temperature rises, glacriers fall and scratches the ground
Evidences for Continental Drift
Matching mountain ranges
Appalachian Mountains of North America and Caledonian Mountains of Scandinavia
Global Tectonics - moving because of —-
lithospheric plates and tectonic plates are the ones cracked and not the continents
radioactive decay
this causes several currents that moves the plates
fracture that separates one plate from another
plate boundary
plate boundary
- moves apart
- causing ridges
divergent
plate boundary
- move towards each other
- causing trenches
convergent
3 Kinds of Convergent Boundaries
a. oceanic and continental
b. oceanic and oceanic
c. continental and continenal
a. oceanic crust sinks; trench and volcano on continental crust
b. based on rate of movement (faster - floats; slower - subducts), based on age (older plate sinks); trench and volcanic island arc
c. mountains form, no formation of volcanoes
plate boundary
- two plates slide horizontally past one another as they move in opposite directions
- frequent earthquakes
transform
Supercontinents and Age
Ur 3 bya
Kenorland 2.5 bya
Nuna/ Columbia 1.8 bya
Rodinia 1.1 bya
Pangea 240 mya
