Answer: Heidi Doody. Heidi Doody was built by Margo Rose and had the voice of Norma MacMillan and Donna Miller. Heidi was introduced as a stranger who saved Buffalo Bob's life in Africa. Later, Heidi was adopted and became Howdy's sister.
The descending of rock layers at subduction zones causes metamorphism in two ways; the shearing effect of the plates sliding past each other causes the rocks coming in contact with the descending rocks to change. Some of the descending rock will melt because of this friction.
Geothermal gradients in the earth caused by radioactive decay are the most common cause of temperature differences and thus a cause of metamorphism. As a general rule, heat increases as depth into the earth increases. The gradient creates different types of rocks at different depths.