Mountains and Groundwater

[Carrikature]

Most underground rivers are due to cavernous limestone regions and not permeability of the rock itself. Limestone is often relatively impervious, but dissolves to form cavernous and cracked formations.

I was talking about the overall composition of what's below the surface, not traits of specific aspects of that composition.

[Teallaura]

It does. I just threw that bit of trivia in to mess you up.

[shunyadragon]

Not true in the case of the Mojave River.

Please note; I said most. Actually I was not specifically aware of the Mojave River geology and I had to do some homework.

The Mojave River is a rare case of a closed basin river system cut off from the an ancient drainage that flowed toward the Pacific by a mountain building event ~10 million years or more in the past. It is a desert environment with a weathered sandstone and limestone and alluvial strata underneath it. This creates an environment where in areas of weathered bedrock and alluvial deposits the river flows under the surface in part because the river no longer erodes a deeper channel in the weathered material because it no longer has an outlet to the sea. In contrast this uplift increased the channel erosion of the Colorado River and created a vaste canyon with an outlet to the sea.

The Mojave river system is a classic example of evidence supporting and ancient geologic series of events and an earth with hundreds of millions of years of geologic history.

[DesertBerean]

[shunyadragon]

I was talking about the overall composition of what's below the surface, not traits of specific aspects of that composition.

I have been addressing the differences and why the groundwater is different in different regions. The traits of the composition of the underlying strata is why the amount of groundwater is different regions. Limestone karst geology is one of the characteristic of major regions of the world with extensive groundwater. The Mojave River basin is not characteristic of a region, except in general it is part of a Dessert Basin Region of the Great Basin including Death Valley where limited recharge of the groundwater takes place due to being an arid region.