Earth's Changing Surface — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. Earth's outer layer is broken into large pieces that slowly move. What are these pieces called?
A) Tectonic plates
B) Sediment layers
C) Glaciers
D) Volcanoes
Earth's surface is broken into tectonic plates that move slowly and cause many of the changes we see.
2. What usually happens when two tectonic plates push directly into each other on land?
A) Mountains form as rock is pushed upward
B) A flat plain forms quickly
C) The plates disappear into the air
D) A new ocean forms between them
When plates push together (converge), rock is squeezed and folded upward, building mountain ranges over millions of years.
3. What forms when two plates pull apart from each other on land?
A) A rift valley with a deep crack
B) A tall fold mountain
C) A sandy beach
D) A canyon carved by a river
When plates pull apart (diverge) on land, the crust thins and drops down, forming long rift valleys like East Africa's.
4. California's San Andreas Fault is famous because two plates ___ each other along it, often causing earthquakes.
A) slide past
B) stack on top of
C) freeze together with
D) melt into
Where plates slide past each other (transform boundary), stress builds up and is released as earthquakes.
Part B: Fill in the Blank
Write the correct answer on each line.
1. The large moving pieces of Earth's outer layer are called tectonic plates.
Tectonic plates are the giant rock slabs whose motion creates mountains, earthquakes, and volcanoes.
2. When plates push together and one bends down under the other, the deep crack underwater is called a trench.
Ocean trenches form at converging plate boundaries where one plate slides under another (subduction).
3. A long crack in Earth's crust where plates can move past each other is called a fault.
Faults are weak zones in the crust where most earthquakes happen as stuck plates suddenly slip.
4. Mountains, volcanoes, and earthquakes are mostly caused by the slow motion of Earth's plates.
Plate motion is the big idea behind almost every major Earth-surface feature studied in Grade 4.
5. When melted rock from inside Earth pushes up through a plate boundary and erupts, it builds a volcano.
Many volcanoes form along plate boundaries where magma can rise through cracks in the crust.