Crust (geology) depth, reaching values typically in the range from about to at the boundary with the underlying mantle. The temperature increases by as much as for every kilometer locally in the upper part of the crust, but the geothermal gradient is smaller in deeper crust. The continental crust has an average composition similar to that of andesite. The most abundant minerals in Earth's continental crust are feldspars, which make up about 41% of the crust by weight, followed by quartz at 12%, and pyroxenes at 11%. Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much
The Menace from Earth The Menace from Earth "The Menace From Earth" is a science fiction short story by American writer Robert A. Heinlein, first published in the August 1957 issue of "The Magazine of Fantasy & Science Fiction". The story is set in the near future, when the Moon is colonized with people living in underground cities. The "menace" of the title is a glamorous woman tourist who visits the Moon colony. She is assigned a young guide named Holly, a 15-year-old girl and aspiring starship designer who is the first-person narrator. Holly's best friend Jeff develops a crush on the "groundhog" visitor,