Lava, or ________ rock, often flows out of a volcano during an eruption.
frozen
moist
dessicated
molten
An understanding of ________________ has helped explain how and why earthquakes occur.
history
meteorology
plate tectonics
oceans
All of Earth’s continents were once joined together in one large ___________.
island
plate
ocean
landmass
___________________ continues to cause areas like North America and Africa to move farther apart.
Island slide
Continental drift
Earthquake shaking
The Pacific Ocean
The Earth's ________ is a rocky shell that measures about 2,900 kilometers thick.
core
layer
crust
mantle
A major ______________ runs through California, which is why they have a lot of big earthquakes.
glacier
fault line
plate
crack
Rivers often serve as natural __________, separating one piece of land from another.
bridges
walls
gates
boundaries
Many people were amazed when Jake's ____________ about the future became true.
guesses
ideas
predictions
plans
Running is one activity that requires a lot of ________.
strength
power
practice
energy
Many American _______________ have trails that allow hikers to climb across several mountains.
mountain ranges
valleys
foothills
canyons