The Basin and Range Province is a broad region
of parallel north-south oriented
valleys (known as basins) and surrounding mountains ranges.
The province was created as this area of The
North American plate was stretched, fractured
and broken into hundreds of mountain blocks.
Lets watch a hypothetical block undergo early
rifting.
Both sides of the area under tension pull
apart evenly.
Hot material from the asthenosphere migrates
upward causing the land surface to rise and
break along fault lines into basins and ranges.
Heat from the asthenosphere warms the upper
mantle and lower crust facilitating ductile
deformation, thus allowing this lower part
of the plate to stretch and pull thinner like
taffy.
The buoyancy of the warm material in concert
with the thinning of the plate contribute
to continued upward movement creating fault-bound
valleys and up-faulted mountain ranges.
This is considered by some to represent early
onset of rifting.
