Upgrade to remove ads
EARTH2-12: Earth's History
Terms in this set (42)
EON: "hell", from 4.57 to 3.8 GA
-Formation of the moon, oceans, and atmosphere
EON: "ancient", from 3.8 to 2.5 GA
-Birth of continents
-Appearance of the earliest life forms.
EON: "before life", from 2.5 to .542 GA
-Development of plate tectonics
-buildup of atmospheric O2, multicellular life appears.
EON: "visible life", from 542 Ma to present.
-life diversified rapidly.
What are the boundaries that helped date the hadean?
the age of the earth, based on the ages of chondrite meteorites
-the average age of the oldest continental crustal rocks.
-Began with formation of earth by planetesimal accretion.
What was earth like during the hadean?
Earth was heated by impacts and radioactive decay causing earth to be insanely hot. earth was hot enough to partially melt by 4.5 GA
The molten earth underwent chemical differentialtion.
describe earths structure during hadean and how it was formed.
gravity pulled molten iron into the center, forming the core. the ultramfic mantle remained as a thick outer shell.
how was the moon formed?
there was a protoplanet impact that blasted a huge chunk of earths mantle and much of the protoplanets mantle into orbit. this formed debris around the earth, which eventually coalesced to form the moon.
earliest evidence of solidified igneous rock?
from 4.4 Ga, before that earth was inhospitable.
-can tell from zircon grans, not a whole rock geochronology.
How did the first oceans form?
-they formed as rain from the skies....this was evidence that the earths surface was beginning to cool.
what FOUR major things happened during the archean??
1. portions of the rock record began to survive
2. differentiation of continental and oceanic crust
3. primitive plate tectonics.
4. EARLIEST EVIDENCE OF LIFE!
When were the first cratons formed?
by 2.7 GA, during the Archean.
During what eon did the volume of the continental crust increase dramatically and what was its significance?
1. 85% of modern continental area present by the end of archean.
2. by 2.7 Ga, the 1st cratons had formed.
3. May signal development of plate tectonics.
How did continental crust form during the Archean?
There were many small microplates, island arcs, and hot-spot volcanoes, rapidly formed and subducted crust.
-Low density felsic rocks formed above subduction zones.
-felsic crust blocks grew via continental collision and felsic sediments accumulated near continental crust.
-The mantle hot spots built mafic volcanoes.
**continental crust is too buoyant to subduct and when they collided together they continued to build upon eachother and built protocontinents. :D like a big ice cream scoop.
alternate hypotheses to how continents were formed?
the archean lithosphere was too hot to subduct, and hot=spot plume volcanism dominated crustal formation until the late Archean.
Evidence of first life during the Archean?
-Preserved fossil cells.
When were the oldest undisputed bacteria fossils found to be from?
What are stromatolites?
fossils of the layered mats of the cyanobacteria and the minerals holding the layers together
-PHOTOSYNTHETIC! CO2+H20>>organic matter+O2
what is cyanobacteria?
blue green algae found in stromatolites....in the archean.
What eon was the transition from archean world to "modern" earth?
What main three things happened during the proterozoic?
1. fewer, larger lithospheric plates.
2. Larger continental landmasses
3. an oxygenated atmosphere.
what was going on with the continents during the proterozoic?
-90% of Earths continental crust by the middle of it.
-continents grew by addition of volcanic arcs.
-continents cooled and strengthened to become cratons.
what was going on with north america during the proterozoic?
The craton consists of many distinct blocks:
-sutured archean crustal blocks form the interior.
-volcanic arcs and crustal slivers were added to margins.
What were the two main supercontinents in the proterozic?
**Supercontinent in proterozoic
-formed 1Ga, broke apart 700 Ma
-Greenville orogeny formed an extensive mountain belt.
**Supercontinent in proterozoic
-a short lived supercontinent, about 600 Ma
what happened with the oxygen levels in the Proterozoic? what did this....make?
it skyrocketed due to photosynthesis. (from about 2.4 to 2.2 Ga)
-Redbeds, or iron-oxides appeared after 2.2 Ga
how are iron oxide deposits created?
Fe dissolved in the ocean and reacted with O2, forming world wide iron oxide deposits!! :D
what did higher levels of O2 in the Proterozoic permit?
1. multicellular organisms! :D
aerobic respiration was efficient.
2. O2 made formation of the ozone layer possible.
what does the ozone layer do?
it absorbs deadly ultraviolet (UV) radiation.
from the Proterozoic
-unusual soft-bodied fossils.
-preserved in end Proterozoic sediments 600-542 Ma
-multicelluar invertebrates resembling worms and jellyfish.
what two global events happened during the Proterozoic?
1. the assembly and breakup of the pannotia
2. "snowball earth": extreme global cooling. ice covered the land, possibly even froze the oceans. life diversified rapidly after snowball conditions waned.
Precambrian (time?? something) consists of what eons?
Hadean, Archean, Proterozoic
What happened with shells and fossils during the Phanerozoic?
-There were diverse hard-shelled organisms.
-hard shells vastly increased fossil preservation.
-made possible a more complete archive of life on earth.
early paleozoic consisted of what periods?
Cambrian and Ordovician
Rifting of pannotia left for large continental fragments during the early paleozic. what were they?
1. Gondwana-(SA, Africa,Anarctica, India, Austrailia)
North america in the early paleozoic?
-the rifted continents developed passive margins
-rising seas flooded expanses of continental crust.
-Epicontinental seas were shallow, warm, and sunlit...GREAT CONDITIONS FOR LIFE!
"the Cambrian explosion"?
RAPID DIVERSIFICATION IN THE EARLY PALEOZOIC!
-Earliest cambrian-Hard shells appeared for the 1st time.
-Reflects the evolution of a complex ecosystem. (plankton, deposit feeders, giant predators ect)
what where several "firsts" during the Ordocivian...in the early paleozic...
1. Vertebrates (agnathans -jawless fish)
2. Crinoids (flower like echinoderms)
3. Green algae and primitive land plants.
what is kind of funny about where life was located....during the early paleozoic?
there were loads of diverse life in the ocean from no animal life on land!
THIS SET IS OFTEN IN FOLDERS WITH...
Chapter 7- Deformation: Modification of…
geologic time , crustal deformation
Precambrian Earth and Life History chapter 19
YOU MIGHT ALSO LIKE...
Geol 1003 Ch. 11 The Hadean and Archean Eons of Pr…
Geo Time Quiz
Ch. 22 Study Guide
OTHER SETS BY THIS CREATOR
V E R B S
VOCABULARY From book
PRESENT TENSE: stem changing verbs and verbs with…
OTHER QUIZLET SETS
The Odyssey Study Guide Books 19-21
(Exam 3) Hyperemesis, ectopic pregnancy, hydadtifo…
NTRI 2000-001 Final Exam Study Guide