A local rock collector claims that she has found the first example of pyroxene and sodium-rich feldspar in the same rock. Write a commentary about her claim for publication in a rock collector society newsletter.

The rock containing clinopyroxene and plagioclase (a type of feldspar) is called either basalt (fine grained extrusive rock) or gabbro (coarse grained intrusive rock). The plagioclase is generally calcium rich i.e. anorthite rich. But rock contains sodium rich feldspar. This means the sodium has replaced calcium. This replacement occurs in underwater (in oceans/seas) extrusion of basalt where sodium from seawater replaces the calcium in anorthite rich plagioclase feldspar. The altered basalt due to sodium exchange is called spilite which contains sodium rich feldspar and pyroxene.

Explanation:

the denominator has a very specific role.

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.