I got the first one but I cant get this one can someone help me.... It says that I have to measure the distance between the continents along an east-west line fron the eastern edge of Brazil directly east to Africa.... It says that I have to divide the distance in centimeters seperating the continents and the rate of seafloor spreading. The rate of sea floor spreading is 3.9 cm/yr..... If someone can help me this I would be truely appreciated. I just cant get the answer to this one problem....
2007-03-08 04:39:38 · 3 answers · asked by skibailey56 1 in Science & Mathematics ➔ Earth Sciences & Geology
I'm just going to estimate that the width of the south atlantic from Brazil directly east to Africa is about 3200 km. There are 100,000 cm in a one km, so that means that Brazil and west Africa are about 320,000,000 cm appart. Divide that by 3.9 and you get about 82 million... so, using this method you come up with an answer of ~82 million years ago.
Be aware that this was based on my estimate, and the south atlantic spreading center has been active for over 100 million years in some places. But in the area in question, the oldest rock is between 84 and 117 million years old according to the map in my geology textbook.
2007-03-08 05:38:29 · answer #1 · answered by brooks b 4 · 0⤊ 0⤋
Although this method will work it makes two assumptions that may not be valid. The first assumption is that South America and Africa have been diverging in a straight line, exactly east-west. The next assumption is that the spreading rate has remained constant at 3.9 cm/yr. By the Jurassic, rifting had begun and largely during the Cretaceous. That time frame is about 140 Ma (mega annum or million years) to 80 Ma.
2007-03-08 06:51:59 · answer #2 · answered by Amphibolite 7 · 1⤊ 0⤋
That's not true
2016-09-20 00:25:22 · answer #3 · answered by alix 4 · 0⤊ 0⤋