The south american and african plates moved apart as a divergent boundary formed between them and an ocean basin formed and spread Earth's plates move on top of a soft, solid layer of rock called the mantle. Although the african plate's northeastward absolute motion slowed abruptly 30 million years ago, the south atlantic's spreading velocity has remained roughly constant over the past 80 million years, thus requiring a simultaneous westward acceleration of the south american plate. On the west side of south america, it experiences devastating earthquakes due to the convergent plate tectonic boundaries But the eastern edge lies in the atlantic ocean at a divergent plate boundary Along the african plate boundary, these two plate boundaries pull apart from each other.
Earth’s plates move on top of a soft, solid layer of rock called the mantle At divergent plate boundaries, rock rises from the mantle and hardens, adding new old rock to the edges of both plates At convergent plate boundaries, one plate moves underneath the other plate and sinks into the mantle. The explanation is that plates rotate as they move Scientists now have a fairly good understanding of how the plates move and how such movements relate to earthquake activity There are four types of plate boundaries:
Because these two plates are moving away from each other, this represents a divergent plate boundary. Sediment that has accumulated on the continental slope is thrust up into an accretionary wedge, and compression leads to thrusting within the continental plate (figure 10.4.7).
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