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