opreading Activity 2.6 Course/Section Date: AThe map of the northern Atdantic Oc
ID: 116327 • Letter: O
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opreading Activity 2.6 Course/Section Date: AThe map of the northern Atdantic Ocean Basin (Fig. A26.1) shows isochrons (lines of equal age) of the buasaltic crust beneath the sediments that have accumulated on the seafloor. These isochrons were derived by Maria Seton an colleagues (2012) from an analysis of marine magnetic anomalies, and their ages are based on the geomagnetic polarity time scale. GPlates (http:/ of the divergent boundary the axis of the mid-ocean ridge-between the North American and African scale. GPlates (http:/ www.gplates.org) was used to help make this map. The red line on the map shoms the location Plates 30 W North American Plate African Plate NA 1500 km 154.3 M (M25) approximate scale at center of map Figure A2.6.1 The approximate great-circle distances between the points identified on the map are listed here. The uncertainty in the distances provided is probably on the order of 10 km. CNA to B Bua to A Bas to A 1354 km 1338 km 1320 km 1279 km 2617 km 2599 km 2649 kum 5107 km Car to A B to Bu A drifted away frorn the ndge at A during the past 67.7 Myr expressed in cn/yd 1. What is the average speed at which What is the average speed that Bus drifted from A? Which plate mosed faster relative to the ridge over the past 67.7 Myr, if cither? cm/yr area between Css and B consists of oceanic lithosphere added along the Mid-Atlantic Ridge to the North American North American Plate along that line?m/yr. 2. The Plate between 154.3 and 67.7 Myr. What is the average speed at which new lithosphere was added to the lithosphere was added to the African Plate along that line? -an/yt Which plate moved faster relative to the ridge between 154.3 and 67.7 Myr, if eitheri Do the same analysis for the lithosphere berween points Gar and Bu. What is the average speed at which new 65Explanation / Answer
A)
1) The average speed at which BNA drifted drifted away from the ridge A is = d/t
here d = 1338 km = 1338 * 106 cm
t = 67.7 * 106 years
Average speed = 1338 * 106/67.7 * 106
= 19.76cm/yr
The average speed of BAF drifted away from A is
d = 1320 km = 1320 * 106 cm
t = 67.7 * 106 years
Average speed = 1320 * 106/67.7 * 106
= 19.49cm/yr
Plate BNA move faster than BAF releative to ridge over the past 67.7 Myr.
2) The average speed at which new lithosphere was added to the north american plate is = d/t
here d = 1354 km = 1354 * 106 cm
t = 154.3-67.7 = 86.6Myr = 86.6 * 106 years
Average Speed = 1354 * 106/86.6 * 106
= 15.63 cm/yr
The average speed at which new lithosphere was added to the african plate is = d/t
d= 1279 km = 1279 * 106 cm
t = 154.3-67.7 = 86.6Myr = 86.6 * 106 years
Average speed = 1279 * 106/86.6 * 106
= 14.76 cm/yr
Plate BNA move faster as compared to plate BAF relative to the ridge between 154.3 and 67.7 Myr.
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