Unit-2 GeosphereActivity 2A- Plates and Gates

Background Information for the Teacher

4d: Scientific observations indicate that global climate has changed in the past, is changing now, and will change in the future.7e: Ecosystems on land and in the ocean have been and will continue to be disturbed by climate change. Animals, plants, bacteria, and viruses will migrate to new areas with favorable climate conditions.

Geosphere 1c: Processes arising from plate tectonics, such as earthquakes and volcanism, can have direct and profound effects on the other Earth systems. Geosphere 3a: The topography of the seafloor, formed by plate tectonics and sediment deposition, affects the flow path of deep ocean currents.Geosphere 3b: The topography of the land, shaped by plate tectonics, weathering, erosion and sediment deposition, affects the flow path of atmospheric currents.

NSES CLEP

ELF

Activity

In this hands-on activity, learners create a time line and explore a story to show how continental drift and plate movement has altered continent location, ocean currents, and therefore climates over geologic time. The story of octopus species development around Antarctica is used to illustrate the change in the climate as the Drake Passage opened up. With a continuous ocean current blocking Antarctica from heat flowing from the lower latitudes its climate dramatically changed.

Std B: Heat moves in predictable ways, flowing from warmer objects to cooler ones.Std C: Although different species might look dissimilar, the unity among organisms becomes apparent from the evidence of common ancestry.Biological evolution accounts for the diversity of species developed through gradual processes over many generations. Std D Lithospheric plates on the scales of continents and oceans constantly move at rates of centimeters per year in response to movement in the mantle. Fossils provide important evidence of how life and environmental conditions have changed.

2a: Earth’s climate is influenced by interactions involving the Sun, ocean, atmosphere, clouds, ice, land, and life. Climate varies by region as a result of local differences in these interactions.2b: Changes in ocean circulation caused by tectonic movements or large influxes of fresh water from melting polar ice can lead to significant and even abrupt changes in climate, both locally and on global scales.3a: Individual organisms survive within specific ranges of temperature, precipitation, humidity and sunlight. Organisms exposed to climate conditions outside their normal ranges must adapt or migrate, or they will perish.3c: The distribution patterns of fossils show evidence of gradual as well as abrupt extinctions related to climate change in the past.4a: Climate can be described for different time intervals, such as decades, years, seasons, months, or specific dates of the year.

CLEP

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Unit-2 GeosphereActivity 2A- Plates and Gates

Photo credit: M. Rauschert (M. setebos).

Megaleledone setebos--A shallow water species of octopus found all around Antarctica and only in the Southern Ocean. It is a close relative of the deep sea species.

The specimen shown is a juvenile. Adults reach a total length of nearly 1 meter. (about one yard)

To learn more:

Strugnell, J., Rogers, A.D., Prodöhl, P.A., Collins, M.A. & Allcock, A.L. (2008) The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses. Cladistics. 24: 853-860.

NSES: National Science Education Standards (http://www.csun.edu/science/ref/curriculum/reforms/nses/index.html) CLEP: Climate Literacy Essential Principles (http://www.climatescience.gov/Library/Literacy/) ELF: Environmental Literacy Framework (www.andrill.org/education/elf)

For more information: NASA animation of plates moving apart, similar to diagrams http://www.nasa.gov/audience/forstudents/5-8/features/F_Earth_Has_Faults_prt.htm http://oceanexplorer.noaa.gov/edu/learning/1_plate_tectonics/plate_tectonics.html#slide Video of ice increase / decrease Antarctica http://www.youtube.com/watch?v=mQwxa47x5VU

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Unit-2 GeosphereActivity 2A- Plates and Gates

Background Information for Teachers

The word tectonics comes from the Greek root "to build," and “plate”, which means a large slab. The two words together, create the term plate tectonics, which refers to how the Earth's surface is composed of plates. The Earth's uppermost layer of Earth’s crust is fragmented into about a dozen large and small plates that are moving relative to one another as they float atop molten material below. As people began to see the shape of the continents on the Earth, they believed that the present-day positions were part of a preexisting larger landmass termed supercontinents. Called Pangaea, this supercontinent was the birthplace of all the other continents and began to break up between 225-200 million years ago (mya).

The idea that the continents moved over geologic time was largely developed by the German scientist, Alfred L. Wegener, who suggested that the Earth's continents were once joined into supercontinents. In 1912, Wegener stated that all the present continents were previously one large continent, but then broke apart due to shifting of the landmasses. Two other viewpoints prevailed at this time, so Wegener’s thoughts were not readily accepted. Many believed that the continents and ocean basins were unchanged since they formed. Others believed that the Earth was slowly contracting and as this occurred, ocean floors became dry land, and dry land in turn became ocean floor.

In the 1960s, the theory of plate tectonics began a change in the thinking about our Earth. The idea that the Earth's surface is continually moving has profoundly changed the way we view our world. It took the work of many scientists and technicians gathering data from many sources to confirm how the continents have been shaped by plate-tectonic processes.

Wegener used the fossil record and similarity in rock layers as evidence. When Wegener presented the evidence that the fossil plant Glossopteris was found on more than one disconnected land mass, this supported his theory that the continents were once connected. In the 1960's, sequences of rock were discovered in Antarctica that were similar to those on other continents confirming Wegener's theory. By the 1970's, a rapid growth of space-based techniques for taking precise, repeated measurements provided more data for scientists to study the movement of the plates.

Current plate movement can be measured by means of ground-based or space-based measurements. Geodesy is the science of the size and shape of the Earth. Ground-based measurements are taken with conventional and very precise laser-electronic instruments. However, because plate motions are global in scale, the best measurements are satellite-based.

Space-geodetic measurements have already confirmed that the rates and direction of plate movement, averaged over the several current years of data collection, confirm with rates and direction of plate movement averaged over millions of years. Not all the plates move at the same rate. The African plate moves about 25 mm per year, whereas the Australian plate moves about 60 mm per year.

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