6th grade vocabulary Earth Science Unit
1. Mineral-element or compound, formed by nature but not formed by living things, that has a
specific crystal structure and physical and chemical properties
2. Rock-hard and compact mixture of minerals that formed naturally
3. Rock cycle-process by which rocks, over geologic ages, can be changed into different kinds of
rock
4. Mohs hardness scale-a system listing ten minerals that the hardness of other minerals can be
compared with
5. Plate tectonics-theory that describes and explains the way that continents separated into
today’s land masses from one large ancestral land mass (Pangea)
6. Luster-how the surface of a mineral appears when it reflects light
7. Sedimentary rock-rock formed when sediment is pressed and cemented together naturally, over
millions of years
8. Igneous rock-one of three main kind of rock, made from cooled magma
9. Metamorphic rock-rocks that have been changed over time by high pressures and temperatures
inside Earth’s crust
10. Crust-outermost, rocky layer of Earth
11. Mantle-a layer of Earth’s surface, lying just below the crust and above the inner core
12. Inner core-innermost part of Earth, made of solid iron and nickel
13. Outer core-layer inside Earth, between the mantle and inner core, which has some properties of
a liquid
14. Asthenosphere-layer in the upper part of Earth’s mantle that is made of material that can be
reshaped and deformed, and on which the continents move
15. Lithosphere-outermost layer of Earth’s surface, which is rocky and solid, includes the crust and
the rigid part of the upper mantle
16. Transform boundary-boundary between two lithospheric plates where the plates are sliding
past each other
17. Convergent boundary-formed where two sections of Earth’s crust are colliding
18. Divergent boundary-forms where lithospheric plates are moving away from each other
19. Subduction-the process in which one lithospheric plate slides under another; occurs at
converging plate boundaries