Plates I Activity 2: Magnetic Reversals and Sea Floor Striping f. Label the age
ID: 286337 • Letter: P
Question
Plates I Activity 2: Magnetic Reversals and Sea Floor Striping f. Label the age of each isochron (solid line) at the bottom of the right-hand side of the map using the information recorded on your ocean-floor map. 2. Assuming the distance to the farthest isochron is 300 km, the spreading rate of the ridge was: 300 km Spreading rate. _distanoe my km my Crm yr 3. Using your knowledge of how magnetic anomalies form and Figure 2.10 on page 63 in your textbook, answer the following questions. a. What is the age of the oldest oceanic crust found on Earth? b. Near what major geologic feature of the Earth's surface is older oceanic crust always located? c. How does this compare with the oldest continental rocks? d. Assuming that the Earth is 4.6 billion years old, what percentage of the Earth's history is recorded by the rocks of the ocean basins? Roldest oceanic rock (my)-koo% % Earth's history- age of Earth (my) 4600 my e. Why are there no old rocks found on the ocean floor?Explanation / Answer
3.a. the oldest oceanic crust in the earth is about 180-200 million year ago that is west pacific and north west atlantic.
b. older oceanic crust always located near subduction zone or convergent zone.
d. % earth's history= [oldest oceanic rock (ma)/age of earth(ma)]*100
=[200/4600]*100
=4.348
e. Oceanic crust is continuously being created at mid-ocean ridges. As plates diverge at these ridges, magma rises into the upper mantle and crust. As it moves away from the ridge, the lithosphere becomes cooler and denser, and sediment gradually builds on top of it. The youngest oceanic lithosphere is at the oceanic ridges, and it gets progressively older away from the ridges.The oceanic lithosphere subducts at what are known as convergent boundaries. These boundaries can exist between oceanic lithosphere on one plate and oceanic lithosphere on another, or between oceanic lithosphere on one plate and continental lithosphere on another. In the second situation, the oceanic lithosphere always subducts because the continental lithosphere is less dense. The subduction process consumes older oceanic lithosphere, so oceanic crust is seldom more than 200 million years old.
g. north atlantic ocean begin to open up 160 million year ago.
k.north atlantic ocean begin to open up 130 million year ago