Author Question: What are the forces that are thought to cause movement of lithospheric plates in plate tectonics? ... (Read 54 times)

melly21297 · **on:** Jul 15, 2018

What are the forces that are thought to cause movement of lithospheric plates in plate tectonics? What will be an ideal response?

Question 2

What is the significance of the alignment of seamounts and islands of the Hawaii-Emperor Seamount
chain and other similarly oriented alignments to the south (e.g., Tuamotu Islands and Line (Austral)
Islands)? What will be an ideal response?

fffftttt · **Reply #1 on:** Jul 15, 2018

Answer to Question 1

Thermal convection produces upwelling at divergent plate boundaries and outward flow directly away
from them. This is believed to contribute to the motion of overlying plates in the sense that they are
carried or dragged along by these currents. Heating of the axis of a divergent boundary causes thermal
expansion that elevates the Mid-Ocean Ridge system, thus creating a slope. This slope brings into play
gravitational forces that tend to move the lithospheric plates downslope away from the ridge axis. In
addition, older oceanic lithosphere is thought to be colder, thicker, and hence heavier than younger
lithosphere and thus tends to sink more readily. This can be seen in the ocean-ocean convergent
boundary at the Mariana Trench where the much older western part of the Pacific plate plunges under
the younger Philippine plate

Answer to Question 2

All are thought to be aligned volcanic chains that were produced at hot spots. The straightness and
parallelism of these alignments is considered to represent the direction of absolute plate motion. The
bend in each chain implies that there was a relatively abrupt change in the direction of plate motion or
a clockwise rotation of the Pacific plate about 40 million years ago