TheDevonianPeriod

417 to 354 Million Years Ago

DEVONIAN CONTINENT

EARLY DEVONIANClimate: Average 30 °C

86 °F

Atmosphere: High in Oxygen

Landscape:

Many plants grew without roots or leaves.

Heights ranged from 1 in – 3 ft tall

Red land due to inorganic soil

Vast ocean

Zosterophylls

Trimerophytes

MIDDLE DEVONIANClimate: Cooling 5 °C

41 °F

Equator ran through Arctic Canada where the rainy belt flourished land plants.

Warm shallow seas and cloudless skies were the conditions of North America, Australia and Siberia.

Atmosphere: CO2 depleted. It is believed that it was a result of the cooling.

Landscape: Shrub-like forests of primitive plants existed

LATE DEVONIAN

Climate: Average 30 °C86 °F

Very similar to early Devonian climate.

Atmosphere: Very Dry

Landscape:

First glaciers of the period formed when ice began to cover parts of the South Polar region.

Trees were reaching the heights of 30 feet with intricate root systems.

MASS EXTINCTION3 Major Extinctions:

Taghanic Event - the extinction of corals and brachiopods (bivalve ocean dwellers). This was once considered the boundary for Middle and Late Devonian.

Kellwasser Event - the extinction of the goniatite groups, many conodont species, most colonial corals, several groups of trilobites, and brachiopods.

Hangenberg Event - the extinction of some trilobites, several groups of goniatites, and the unusual late Devonian coiled cephalopods.

Causes include asteroid impacts, global anoxia (widespread dissolved oxygen shortages), plate tectonics, sea level changes (glaciation) and climate change. The reasoning behind these causes revolves around black shale deposits in the extinction areas.

400

370

PLATE TECTONICS

Euramerica and Gondwana shifted north.

The majority of the Devonian Period, large areas of North America and Europe, South America, and Australia were covered by seas, which withdrew during the Upper Devonian.

As the ocean between Euramerica and Gondwana closed, the formation of Pangea initiated.

What Changed?

Works Cited

"Devonian : Climate and Tectonics during the Devonian." Paleobiology Home. Web. 16 Mar. 2011. <http://paleobiology.si.edu/geotime/main/devonian5.html>.

"Devonian." Home Page. Web. 16 Mar. 2011. <http://www.scotese.com/>.

"Devonian." Www2.nau.edu. Web. 16 Mar. 2011. <http://jan.ucc.nau.edu/~rcb7/Devonian.html>.

"Early Devonian." Palaeos.org. 2 Jan. 2010. Web. 16 Mar. 2011. <http://www.palaeos.org/Early_Devonian>.

"Global Warming Potential Lecture." The Global Change Program at the University of Michigan. Web. 16 Mar. 2011. <http://www.globalchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/global_warming_potential/index.html>.

"Plate Tectonics." Humboldt State University. Web. 16 Mar. 2011. <http://www.humboldt.edu/natmus/lifeThroughTime/PlateMaps/Devonian/DevonPlates.htm>.