THE EFFECT OF GRAVITY ON ICE SHEET DYNAMICS AND ITS SUPPORT FOR PHLEGRA MONTES' GLACIAL HISTORY

To compare the dynamics of past and active glaciers on Earth and other planets, an expression is derived that highlights the effect of gravity on ice sheet thickness and rate of flow:

μ_fρ_igh_i² ∝ η_iv

where μ_f is the coefficient of friction, ρ_i is density of the ice, g is gravitational acceleration, h_i is thickness of the ice sheet, η_i is viscosity of the ice, and v is velocity of the surface of the ice.

The expression establishes a proportionality between the frictional and viscous stresses that cause the glacier to spread and advance. This will prove useful in future glacial geophysical applications such as determining how ice sheets move, change in size, and deform landscapes on other planets, even where the ice is not made of water. It was determined that gravitational acceleration has an inverse and exponential effect on the thickness of an ice sheet and a direct effect on the rate at which ice flows. Therefore on Mars, where the effect of gravity is less than that of Earth, ice sheets should be thicker and slower-spreading.

This provides support for the hypothesis that the southern region of Phlegra Montes, located around 33°N/162°E, was partly shaped by glacial activity. The region is long-thought to be associated with glaciers due to the physical resemblances it has to glacial landforms on Earth, such as the Ronkonkoma Moraine, a recessional moraine on Long Island, NY. The landform’s large scale implies solely tectonic origins, but localized glacial processes are also viable under the assumption that a massive landform could be the product of an equally massive ice sheet. The region of focus within Phlegra Montes is consequently reinterpreted to consist of a recessional moraine that is breached by two converging meltwater channels which flow into an outwash plain.