Page 215 - THE MELANESIA DIASPORA FILE CETAK ISI 10022017

Sea levels have fallen to a maximum of about 150 meters below present day levels.
Consequently, a present day sea depth line of 200 meters is considered an important
threshold for determining the probable migratory routes of early modern humans.

Geological Dynamics and Migration
In geology, the dynamics of topographical surfaces are controlled by two main forces:
• Endogenous: forces occurring from within the earth and powered ultimately by the
movement of molten rock or magma. These drive the movement of tectonic plates
and create volcanoes. Such forces are instrumental in the creation of mountains
and other surface features.
• Exogenous: forces outside the surface of the earth. These include meteorological
activities such as rain and wind which have the power to cause erosion, particularly
through the way rivers shape the landscape. It also includes abrasion of coastlines
by waves and wind. Gravity and earthquakes, meanwhile, cause landslides.
Together, these forces work on the earth’s surface, wearing away at it, and
reducing its height.

The Pacific Rim is a geological region with especially high levels of volcanic and tectonic
activity. Because of this, it is also known as the ring of fire.

The Ring of Fire
is the most active
area in terms of
tectonics, where
it is marked by the
existence of active
volcanoes.

Chapter 5 215

MELANESIA BOOK FA LAYOUT 051216.indd 215 2/10/17 2:10 PM