1.
aluminum: lightweight, silvery metal that can be formed into almost any shape and is rustproof
2.
brass: mixture of copper and zinc
3.
bronze: mixture of copper and tin
4.
cast: a mold or impression of an object
5.
cave: large hollow area in the earth's crust
6.
coal: black or brown rocklike substance found in layers of rock; a fossil fuel
7.
copper: best low-cost elecebltrical conductor available
8.
ductile: can be drawn into wires
9.
extinct: no longer in existence
10.
fossils: preserved remains of plants or animals
11.
geology: study of the structure of the earth
12.
geyser: a spring from which columns of boiling water and steam erupt into the air at intervals
13.
gold: soft, bright yellow metal measured in karats
14.
gold leaf: gold that has been hammered so thin light can pass through it
15.
hot springs: a flow of warm or hot water from the ground
16.
iron: most useful metal
17.
limestone: rock where most caves are found
18.
malleable: can be hammered into thin sheets
19.
mercury: also called quicksilver; only metal that is liquid at room temperature
20.
mold fossil: formed when the mud that jectburies a plant or animal quickly hardens around it
21.
oil: a thick, dark liquid found in the earth
22.
Old Faithful: famous geyser found in Yellowstone National Park
23.
paleontologists: scientists who study fossils
24.
petrified fossils: plant and animal remains that have turned to stone
25.
petroleum: natural state of oil; also called crude oil
26.
print fossil: formed when the mud containing animal tracks, the outlines of leaves and feathers, or the imprint of skin is hardened into rock
27.
radiation: the rays of energy and tiny atomic particles that are given off from radioactive materials
28.
radioactive: gives off rays of energy and tiny particles
29.
silver: best conductor of electricity
30.
spelunker: people who enjoy exploring caves
31.
stalactites: stone formation hanging from the roof of a cave
32.
stalagmites: stone formation growing up from the floor of a cave
33.
steel: iron's most common alloy; used in making tools, ships, , plumbing, and beams for skyscrapers
34.
uranium: silvery-white, radioactive metal; primary source of nuclear power
35.
wooly mammoth: huge hairy elephant that is extinct