Which of the following is evidence of the past existence of glaciers?

a. rift valleys

b. fjords

c. estuaries

d. oceanic ridges

B. fjords ,Glaciers carve fjords in valleys where they travel. A fjord is a long, narrow
valley with steep sides carved by glacial movement. A fjord represents the seaward end of a deeply excavated glacial-trough valley that was partially submerged by drowning after melting of the ice

Geothermic gradient is the rate of increasing temperature with respect to increasing the depth in the earths interior. away from tech tonic plates boundaries, it is about 25-40 c/km (72-87 degrees f/mi) of depth near the surface in most of the world.