INGOMAR MIDDLE SCHOOL SCIENCE TECTONICS NAME

INGOMAR MIDDLE SCHOOL SCIENCE TECTONICS NAME: ______________________
WES DataStreme Ocean: SeaWifs Images Sea Surface Temp Period: ___ Date: _____Score_____/20
Earth Image Ice Extent MyNASA DATA Live Access Sea Surface Heights
World Ocean Data Sets North Atlantic opening Those Puzzling Plates Visible Earth
Recall that Earth's lithosphere is broken into a dozen massive plates (and many smaller ones) that are slowly moving across the face of the globe. All plates, except the Pacific, include parts of continents as well as ocean basins. In some places, plates are spreading apart forming divergent boundaries whereas in other places, plates are coming together forming convergent boundaries. Also, some plates are sliding past one another; these are transform plate boundaries. Important geological processes are associated with plate boundaries including earthquakes, volcanic eruptions, and mountain building. J Visible Earth

J Go to DataStreme Ocean and under "Geological," click on "Bathymetry." The topography of the ocean floor and continents are displayed on this global map produced by NOAA's National Geophysical Data Center (NGDC). Elevations are color-coded in meters above (+) or below (-) mean sea level.
(See the scale to the left of the map.) The map divides the globe into 45 degree by 45 degree squares.

1. Click on the map square that covers most of the South Atlantic Ocean basin. The topographic feature that trends roughly north/south on the ocean floor is a segment of the Mid-Atlantic ridge and marks a divergent plate boundary. (For an enlarged view, click on the image again. Then use the scroll bars to bring the ridge into view.)
The plate to the west of the ridge is moving generally toward the [(west)(east)] and the plate to the east of the ridge is moving generally toward the [(west)(east)].

2. Lava wells up along divergent plate boundaries from Earth's interior, cools and solidifies, adding new oceanic crust to a plate's edge. Within the abutting plates, the crust migrates away from the ridge as new material is added.(Imagine two treadmills end-to-end with their treads moving outward in opposite directions.) From the Mid-Atlantic ridge westward toward the east coast of South America, the age of the oceanic crust [(increases)(does not change)(decreases)].

3.J Return to the NGDC global bathymetry map and click on the map square that includes most of South America and the adjacent Pacific Ocean. Click on the resulting image for enlargement.
Just to the west of South America and paralleling the coast is a narrow zone where the ocean floor is exceptionally [(deep)(shallow)].

4. This [(continental shelf)(trench)] marks a convergent plate boundary where a [(more dense)(less dense)] oceanic plate subducts under a [(more dense)(less dense)] continental plate.

5. The nearby continental topography in the image indicates the possibility that mountain building [(is)(is not)] associated with this plate boundary.

6. Geologically, coasts are either tectonically active (near a plate boundary) or passive. The west coast of South America is [(tectonically active)(passive)].

J DataStreme Ocean Now return to the "Geological" section of the homepage and click on "Current Earthquake Activity" for a global map of the locations of earthquake activity. The map is color-coded for earthquakes that occurred during the past week, or, if chosen, for the last 30 days. The diameter of the location circle increases with the magnitude of the earthquake. (Earthquake magnitude or intensity is a measure of the amplitude of seismic waves and is specified by the Richter scale. The most intense earthquakes rank greater than 8 on the Richter scale.)

7. Click on "Show Last 30 Days of Earthquakes." The map shows earthquakes are most frequent along the margins of the [(Atlantic)(Pacific)(Indian)] Ocean basin. Earthquakes are [(more)(less)] frequent along the Mid-Atlantic ridge than along the Pacific plate margins.

8. The boundaries of tectonic plates are shown faintly on the map in yellow. The majority of earthquakes occur [(along plate boundaries)(in continental interiors)].

J Go to the "Earth System" section on DataStreme Ocean and click on "NASA Earth Observatory." Click on "Natural Hazards" and then on "Unique Imagery" in the list to the right (J Archive). On the page that appears, scroll down the information to the left, and click on "Unique Imagery: Earthquake Spawns Tsunamis." Finally, scroll down under "Other Images for this Event" and click on "Posted: Dec 28, 2004." The regional map shows the location of the earthquake (marked by a red star) that caused the devastating tsunami of 26 December 2004 which killed more than 220,000 people. Also shown on the map are the tectonic features of the area.

9. The Sunda (Java) Trench shows the boundary between the India and Australia Plates (referred to as the Indo-Australian Plate) and the Burma Plate. According to information provided on the map and accompanying text, this is a [(divergent)(convergent)] plate boundary along which the [(India and Australia)(Burma)] plate(s) is (are) undergoing subduction.

J Return again to DataStreme Ocean the "Geological" section and click on "Current Volcanic Activity" for a global map of the locations of volcanic activity. (This may be slow in downloading. If you are unable to download, please refer to Image 1.) Yellow triangles on the map identify ongoing activity and red triangles, if any, pinpoint new activity unrest.

10. Based on this map and the other information you have concerning tectonic plates, it appears that the majority of ongoing volcanic activity is occurring [(along plate boundaries)(in continental interiors)].

11. Return to DataStreme Ocean the "Geological" section and click on "Bathymetry" to return to the NGDC global bathymetry map. Click on the map square west of the U.S. that includes only Pacific Ocean. Click again to enlarge the image. Note that the "Big Island" of Hawaii is located at the southeast end of a chain of many volcanoes on the ocean floor trending toward the northwest. The tops of [(all)(some)] of these volcanoes are above sea level. This volcanic activity is believed to be unlike most volcanic activity in that it is caused by a hot spot (in Earth's mantle) over which a tectonic plate (the Pacific Ocean plate) is sliding.

12. (JSee another hot spot.) NASA topographical image of Surtsey

In the first part of this investigation J depicts the general pattern of marine sediment on the ocean floor. This portion of the investigation explores some aspects of sediment thickness and the relationships among sediment distribution patterns, sediment thickness, and age of the oceanic crust.

13. J World Ocean sediment thickness (image 1: best seen in color), developed at NOAA's National Geophysical Data Center reveals sediment thickness in the ocean and marginal seas. The data used to produce this map came from ocean drilling and seismic reflection profiles. In general, the map shows the thickest sediments to be located in [(coastal margins) (the deep sea)].Please print a copy.

14. In the Western Hemisphere, the thickest sediments appear along the [(western) (eastern)] North and South American coasts, which are tectonically [(active) (passive)].

15.J (Image 1) reveals an east-west band of sediments in the eastern and central equatorial Pacific that is several [(tens) (hundreds) (thousands)] of meters thick.

INGOMAR MIDDLE SCHOOL SCIENCE TECTONICS NAME: ______________________
WES DataStreme Ocean: SeaWifs Images Sea Surface Temp Period: ___ Date: _____Score_____/20
Earth Image Ice Extent MyNASA DATA Live Access Sea Surface Heights
World Ocean Data Sets North Atlantic opening
16. J Crustal Age Atlantic (image 2), also developed at NOAA's National Geophysical Data Center displays the age of the Earth's crust underlying primarily the Atlantic Ocean. The tectonically active Mid-Atlantic Ridge appears as a ragged black line within a red ribbon. The color scale at the bottom of the image indicates that the geological age of Earth's crust increases with distance from the ridge.
This implies that Earth's crust and sediments resting on it are moving [(toward) (away from)] the ridge.

. stal ntic/image/sedthick9.jpgUsing J (image 2) as reference, draw in the location of the Mid-Atlantic Ridge on J (Image 1)
17. The color-coding used in J World Ocean sediment thickness indicates that sediment thickness in the immediate area of the ridge is near [(0) (500) (1000)] m.

18. Because sediment deposition in such a mid-ocean location occurs at a very low rate (perhaps about 5 cm per 1000 years), this sediment thickness [(is) (is not)] consistent with the expected relationship between sediment thickness and the age of the ocean crust.

On Images 1 and 2, draw a straight line between Cape Hatteras, NC and Mauritania, on the West African coast. Imagine that we are onboard an oceanographic ship located on the line directly above the Mid-Atlantic Ridge. Our ship is equipped with a deep-sea bottom sediment sampler, and a fathometer to measure the depth of the ocean water. The fathometer also has enough power not only to detect an acoustic return from the bottom of the ocean, but also a return signal from the basement basalt oceanic crust under the sediment. This allows us to measure the distance from the bottom of the ocean to the top of the oceanic crust, that is, the thickness of the sediments. Also, imagine that we can take sediment cores.

We begin sampling by taking bottom grab samples every 100 km as we steam away from the Mid-Atlantic Ridge toward Cape Hatteras. The first grab, taken at the top of the ridge system, is at a depth of about 2000 m and is empty because we are over a ridge that is so young that essentially no sediment has accumulated yet. We also see from the fathometer that the depth of the water and the depth to the crust are identical, that is, there is no measurable sediment thickness. As we move west-northwest along our trajectory (charted by the line we drew) off the ridge top, the fathometer reports progressively deeper water and increasing thickness of sediments. The sediment is mostly calcareous ooze made up of calcium carbonate shells of foraminifera and other organisms along with a little red clay. (Red clays are silicate minerals with enough iron to rust, accounting for the reddish color.) As we proceed, the water gets deeper as the ocean bottom slopes downward and the sediments get thicker. Finally at a location 600 km from the ridge center, the water depth is 4000 m and the thickness of the sediments is 1400 m. The sediments are still primarily calcareous ooze.

19. Studies of marine sediment deposition rates indicate that a reasonable general estimation is that sediments are sinking through the ocean depths and accumulating on the bottom at a rate of about 5 cm per 1000 yrs.. Assuming this rate, 1400 m (140,000 cm) of sediments would accumulate in____________years.

The length of time computed in Item 19 can also be assumed to be the amount of time for the underlying crust to have moved the 600 km (60 million cm!) from the ridge center. Dividing the distance of crust displacement by the time it took for the displacement gives an estimate of the rate of crustal movement.

20. That is, the crust is moving away from the ridge at the rate of ___________ cm per year.

21. Because the crust is moving away from the ridge, a sediment core acquired 600 km from the ridge would contain sediments deposited
[(only at the coring site location) (originally from as far as 600 km from the coring site)].

22. As can be inferred from Image 2, the crust is moving outward in both directions from the Mid-Atlantic Ridge, so the actual spreading rate of the Atlantic Ocean is about twice the value calculated in Item 20, or _______ cm per yr.
We can also estimate the age of the Atlantic basin. The distance from the spreading center to the edge of the continental margin off Cape Hatteras (i.e., to the edge of the oceanic crust) is about 3200 km. Dividing 3200 km by the rate the crust is moving away from the ridge towards the North American continent (determined in Item 19), the approximate age of the Atlantic Basin is about 150 million years. This age of 150 million years agrees with magnetic evidence, isotopic dating of oceanic crustal rock, similar calculations and other evidence in the Atlantic and in other basins like the Pacific and Indian Oceans. The oldest oceanic rocks found may be as much as 200 million years. The oldest dates from continental crustal rocks are 3-4 billion years, so the current Atlantic Ocean sea floor is considerably younger than the continents.

Continuing data collection along our trajectory toward Cape Hatteras, we notice that the water depth increases as the ship moves away from the Mid-Atlantic Ridge. Depths eventually exceed 4500 m, and the sediments in the bottom grabs are becoming dominated by red clay. There is good reason for this change in the composition of bottom sediments. At an average depth of about 4500 m, seawater is sufficiently cold and acidic to dissolve the calcareous shells of foraminifera and other organisms. The depth of the ocean below which calcium carbonate dissolves and does not accumulate on the ocean floor is called the Carbonate Compensation Depth (CCD). Below the CCD, calcareous shells dissolve whereas red clays remain. This then explains the change of the sediments to red clay in deeper water.

23. So in water shallower than 4500 m, [(red clays) (calcareous oozes)] dominate. But, in water deeper than 4500 m, [(red clays) (calcareous oozes)] dominate.

As we continue our voyage towards Cape Hatteras, our samples indicate a thickening of the red clay sediment layer on the ocean bottom. But we also determine that a layer of limestone underlies the clays and overlies the basaltic crust below.
24. The limestone resulted from the lithification of the calcareous oozes that were deposited [(in place) (and then transported from a location closer to the Mid-Atlantic Ridge)].

25. Image 2 shows that clay sediment thickness increases as the distance between our ship and North America decreases. This implies that the origin of the clays is [(chemical precipitation) (land) (silica-based organisms)].

26. If we pointed our ship in the opposite direction when we were above the Mid-Atlantic Ridge and headed for West Africa, we would have collected a set of observational data quite similar in sequence to what we found on our voyage towards Cape Hatteras.
Hence, because of seafloor spreading, the thickness of sediment on the ocean bottom generally [(decreases) (remains the same) (increases)] with increasing distance from the Mid-Atlantic Ridge.

See an animation of seafloor spreading and the opening of the Atlantic Ocean basin from about 200 million years ago (mya) to the present, To run the animation, initially drag your mouse (holding the left button down) from west to east across the scene. This simulates going backward in time from the present to 200 mya when all the continents were together as the super-continent Pangaea. Then slowly drag your mouse from east to west to go forward in time from 200 mya to the present. As you move forward in time, you will note seafloor spreading on either side of the Mid-Atlantic Ridge (a divergent plate boundary) and the gradual opening of the Atlantic Ocean basin. The age of the oceanic crust is color-coded with the youngest crust at the Mid-Atlantic Ridge and the crust becoming progressively older with distance to the east and west of the ridge. This animation is provided by the PALEOMAP Project 2002.

27-30.Comments on the animation:_____________________________________________________________

Ocean Interactions with Atmosphere and Geosphere	Dust Clouds Across the Atlantic	Human/Ocean Interactions
	True, False (T or F)	Confidence (H, M, L)
Earth's surface has more land than ocean in the Northern Hemisphere and more ocean than land in the Southern Hemisphere.
The ocean is so huge that human activity has no measurable impact on its state or condition.

Mauritania and Senegal in West Africa are located on the western edge of the Sahara desert. As can be inferred from the satellite image, winds across the desert are blowing toward the [(east) (west)] over the ocean surface. As wind speeds diminish, gravity causes the dust particles to settle out of the atmosphere. Also, precipitation washes some of the dust from the atmosphere. By either way, the final repository for much of the dust is the [(land) (ocean)].

32. Some mineral components of the dust particles may function as nutrients in marine ecosystems. For example, a limiting nutrient in some ocean food webs is thought to be iron. One experiment conducted in the South Pacific showed that adding iron to the ocean spurred growth of phytoplankton. Hence, dust from Africa [(may) (could not)] play a role in Atlantic Ocean food webs.

33. J Human/Ocean Interactions:Clusters of white dots in the Sea of Japan (left center of image) and in the Pacific Ocean east of the islands (right center) are lights at sea. Asian fishing fleets use lights at night to attract fish to their nets. The concentrations of sea-borne lights suggest that [(a few) (many)] fishing boats are employed in that area. For the people of these densely populated and mostly rugged lands, the ocean is a [(major) (minor)] source of food.

34. J Understanding Tsunami A striking example of society being impacted by the ocean was demonstrated by the devastation wrought by the Indian Ocean tsunami of 26 December 2004. Go to the DataStreme Ocean, scroll to the "Earth System" section, and click on "NASA Earth Observatory." Click on "Natural Hazards" under "Current Stories," and then scroll down to "Unique Imagery: Earthquake Spawns Tsunami" and click on it. Scroll down to listing of "Other Images for this Event" and click on "Posted: Jan. 12, 2005." Comparison of the two images shows the effects of the tsunami that washed over a narrow peninsula on the coast of Sumatra, Indonesia. Click on the images for an enlargement of the 7 January 2005 view.

35. A comparison of the two views indicate [(probable great loss of life) (permanent change to shorelines due to erosion) (almost total destruction and damage to structures) (all of the above)].