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Home , Baltica, Gondwana, Laurasia, Pangaea, Siberia (continent), Supercontinent

History

Geography 106 LRS Doug Fischer Introduction

– Overview of geologic history • Plate positions over time • Major biogeographic events Earth’s tectonic history

• Gondwanaland – Southern – Formed 650mya • – Northern Continents – Most converged in 400mya as “old ” • Formation of – Late ~ 275 mya Breakup of Pangaea

• Started 180 mya (early ) – Prior to breakup, great mixing of biota – However, regionalization did still occur as it does on (smaller) continents today Breakup of Laurasia

• Separated & N. America 100 mya • rejoined them 75 mya • Intermittent connection via Greenland & Beringia through Tertiary Breakup of Gondwanaland

• 180-160mya Gondwanaland started to split – (/Jurassic) • Mostly finished by 90 mya

152 mya 94 mya and Antilles

• Plate was sandwiched between N&S America between 80 and 20 mya • Formed ring of islands • Landbridge closed ~ 3.5 mya – Great American Interchange

14 mya Biogeographic consequences of • Fragmentation and dispersal of ancestral biota (vicariance) • Changing barriers and coridors – biotic interchange • Speciation and extinction – changing physical and biological conditions Tour of Geologic History The • starts with explosion of species with hard body parts – (Some multi- cellular algae and animals lived at the end of the Precambrian) Paleozoic Cambrian

• Animals with hard-shells appeared in great numbers for the first time • The continents were flooded by shallow seas. • The of had just formed and was located near the South Pole. Ordivician

• ancient oceans separated the barren continents of , , and Gondwana. • The end of the was one of the coldest times in Earth history. Ice covered much of the southern of Gondwana.

• Laurentia collides with Baltica closing the northen branch of the and forming the "" continent. • Coral reefs expand and plants begin to colonize the barren continents. • Photosynthetic sticks on mudflats Devonian

• By the Devonian the early Paleozoic oceans were closing, forming a "pre-Pangea". • Freshwater fish were able to migrate from the southern hemisphere continents to and Europe. • Evolution of wood! Forests grew for the first time in the equatorial of Artic Canada. Early

• During the Early Carboniferous the Paleozoic oceans between Euramerica and Gondwana began to close, forming the Appalachian and Variscan mountains. • An ice cap grew at the South Pole • Four-legged vertebrates evolved in the swamps near the (tree ferns, tree- horsetails, tree club-mosses). Late Carboniferous

• By the Late Carboniferous the continents that make up modern North America and Europe had collided with the southern continents of Gondwana to form the western half of Pangea. • Ice covered much of the southern hemisphere • Vast coal swamps formed along the equator (seed ferns, early , and mosses). Permian

• Vast deserts covered western Pangea during the Permian as reptiles spread across the face of the supercontinent. • , appear. ferns spread across southern continents • 99% of all life perished during the that marked the end of the Paleozoic Era. • Massive due to devegetation of continents Permo-Triassic Boundary

http://palaeo.gly.bris.ac.uk/palaeof http://sens-de-la-vie.com/Images- iles/triassic/triextict.htm dok/doomsday_impact_asteroide_01.jpg • “The Great Dying” - , marine CO2 venting, asteroid impact - multiple stressors likely

Permian over ~100kya to 2mya • ( ancestors) nearly wiped out • 90%+ of all known species, 80%+ of all known genera extinct • Massive reorganization of marine ecosystems - 50:50 dominance of encrusting ecosystems changed

Triassic to 1:3 favoring more complex ecosystems

http://www.msnbc.msn.com/id/15885653/ Mesozoic Mesozoic Triassic

• The supercontinent of Pangea, mostly assembled by the Triassic, allowed land animals to migrate from the South Pole to the North Pole. • Life began to rediversify after the great Permo-Triassic extinction. • Warm-water faunas spread across Tethys. Jurassic

• By the , south-central had assembled. • A wide separated the northern continents from Gondwana. • Though Pangea was intact, the first rumblings of continental break up could be heard.

• The supercontinent of Pangea began to break apart in the . • In the Late Jurassic the Central was a narrow ocean separating from eastern North America. • Eastern Gondwana had begun to separate form Western Gondwana. • First evidence of angiosperms

• During the Cretaceous the South Atlantic Ocean opened. • separated from and raced northward on a collision course with . • Notice that North America was connected to Europe, and that was still joined to . • Angiosperms begin to diversify rapidly, ginkgos and cycads decline K/T extinction

• The bull's eye marks the location of the Chicxulub impact site. • By the the oceans had widened, and India approached the southern margin of Asia. • Massive eruptions of Creatceous– Tertiary Boundary http://en.wikipedia.org/wiki/Image: http://images.forbestraveler.com/media/photos/i Impact_event.jpg nspirations/2007/08/volcano-01-g.jpg • “The Great Dying” - Deccan Traps, marine CO2 venting, asteroid impact - multiple stressors likely over ~100kya to 1mya • wiped out - except for birds • 75%+ of all known species, 50%+ of all known genera extinct

http://science.nationalgeographic.com/science/prehistoric-world/mass-extinction.html Alternating ice ages and interglacials Drying led to expansion of grasslands Cenozoic and huge herds of grazers Warm period - first extensive grasslands and kelp forests

First elephants with trunks, early horses, first appearance of many grasses

Hyaenodon horridus, a large carnivorous

Oldest known of modern orders of , all <20 lbs Eocene

• 50 - 55 million ago India began to collide with Asia forming the and . • Australia, which was attached to Antarctica, began to move rapidly northward.

• 20 million years ago, Antarctica was coverd by ice and the northern continents were cooling rapidly. • The has taken on a "modern" look, but notice that and parts of Asia were flooded by the sea.

• When the Earth is in its "Ice House" climate mode, there is ice at the poles. The polar ice sheet expands and contacts because of variations in the Earth's orbit (). • The last expansion of the polar ice sheets took place about 18,000 years ago. Holocene

• We are entering a new phase of that will ultimately result in the formation of a new Pangea supercontinent in the future. • Global climate is warming because we are leaving an and because we are adding greenhouse gases to the atmosphere. 50 my in the future?

• If we continue present-day plate motions the Atlantic will widen, Africa will collide with Europe closing the Mediterranean, Australia will collide with S.E. Asia, and California will slide northward up the coast to Alaska. Mass Extinctions

• Species continually go extinct

• Five really BIG mass All genera extinctions in the last “Well-defined genera Trend line 540 million years “Big five” mass extinctions Other mass extinctions

http://en.wikipedia.org/wiki/Extinction_event Mass Extinctions

• Current extinction rate is 1000 times higher than usual • Modern mass extinction will rank with the five biggest • Modern mass extinction, expected to wipe out more than 50% The Golden Toad of Costa Rica, extinct since around 1989. Its disappearance has of Earth’s species been attributed to climate change. by 2100…

Dodo and 2000+ other bird species extinct since 1500 AD (http://en.wikipedia.org/wiki/Holocene_extinction_event) Tour of Geologic history

• Sponsored by the Paleomap Project – http://www.scotese.com/ • Additional information available from – UC Museum of Paleontology • http://www.ucmp.berkeley.edu • Click on “Discover the History of Life” – http://www.enchantedlearning.com/subjects/Ge ologictime.html