1 .		Geology is the science that pursues an understanding of __________.
2 .		__________ is the fundamental principle of geology that states "the physical, chemical, and biological laws that operate today have also operated in the geologic past."
3 .		Modern geology began in the late 1700s when James Hutton published his __________.
4 .		Current estimates put the age of Earth at about __________ years.
5 .		Relative dating involves __________.
6 .		All science is based on the fundamental assumption that __________.
7 .		The overall goal of science is to __________.
8 .		A(n) __________ is a well-tested and widely accepted view that best explains certain observable facts.
9 .		Earth's physical environment is traditionally divided into three major parts: the __________.
10 .		The Earth system is powered by energy from two sources: __________ and __________.
11 .		Based on physical properties, Earth's outermost layer, consisting of the crust and uppermost mantle, is a relatively cool, rigid shell called the __________.
12 .		The three rock types are __________.
13 .		The two principal divisions of Earth's surface are the __________ and the __________.
14 .		The __________ form(s) a continuous belt that winds for more than 70,000 kilometers (43,000 miles) around the globe.
15 .		The oceanic crust is composed of dark igneous rocks called __________, while the upper continental crust has an average composition of a __________ rock.
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