Science Chapter 3 - Plate Tectonics
The hypothesis of ___ was that all the continents once were joined as a single supercontinent and have since {drifted} apart.
Continental drift
Most geologists think that the movement of Earth's plates is caused by
Convection currents in the mantle
A continental plate collides with an oceanic plate at a __ boundary
Convergent
The place where two plates come together is known as a
Convergent Boundary ---> <---
A rift valley forms at a
Divergent plate boundary <--- --->
List 2 examples of continents that have drifted apart from each other.
Europe and North America, or Australia and Antarctica, or Africa and South America
Old oceanic crust is more dense than new oceanic crust because it is
Cool;deep-ocean trenches;subduction
T or F Alfred Wegener provided evidence from landforms, fossils, and climate in support of his theory of THE SHRINKING EARTH
False Continental Drift
T or F If subduction occurs faster than oceanic crust can be created, an ocean will EXPAND
False Shrink
T or F Along a DIVERGENT BOUNDARY, two plates slip past each other, moving in opposite directions.
False Transform
Any trace of an ancient organism that has been preserved in rock is called a
Fossil
To support his hypothesis, Alfred Wegener provided evidence from ___, traces of ancient organisms preserved in rock.
Fossils
A collision between two pieces of continental crust at a converging boundary produces a
Mountain range;Andes
Found in all of Earth's oceans;an underwater mountain range, formed by plate tectonics;two tectonic plates meet at a divergent boundary.
Mid-ocean ridges
Wegener believed that the continents had once been joined in one landmass called
Pangaea
the super continent that existed millions of years ago the super continent that existed millions of years ago
Pangaea
The geological theory that states that pieces of Earth's lithosphere are in {constant, slow motion} is the theory of
Plate Tectonics
The formation of volcanoes and mountain ranges can be explained by the theory of
Plate Tectonics;convergent boundary
The lithosphere is broken into sections called ___, which float on top of the asthenosphere.
Plates
What technology did scientists use in the mid- 1900's to map the mid-ocean ridge?
Sonar
The process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle is known as
Subduction
When continental plates pull apart at a divergent boundary on land, a ___ forms.
Rift Valley
According to the theory of plate tectonics, which layer of the earth is broken into separate sections called plates?
The lithosphere
The Himalayas is a mountain range on the border between India and Nepal in Asia. Describe the role of plate tectonics in the formation of the Himalayas
The plate carrying present-day India moved over time and collided with the large plate carrying Europe and Asia. When these two continental plates collided, continental crust was pushed up, creating the Himalayan mountain range.
How are magnetic stripes near mid-ocean ridges evidence for sea-floor spreading?
The stripes show the direction of Earth's magnetic field when the oceanic crust formed. When the {crust cools}, it hardens and the {iron} in it goes in the {direction of Earth's magnetic field}. Sometimes the magnetic field reverses and scientists found the same pattern on the sea-floor on both sides of the mid-ocean ridge.
A place where two plates slip past each other, moving in opposite directions, is known as a
Transform Boundary---> <---
T or F Mid-Ocean ridges form the LONGEST mountain ranges on Earth.
True
T or F Oceanic crust near the mid-ocean ridge is YOUNGER than oceanic crust farther away from the ridge.
True
The continents were once joined together in a single landmass
Wegener's hypothesis of continental drift
Compare and contrast what occurs when two oceanic plates collide, when two continental plates collide, and when an oceanic and a continental plate collide.
When 2 oceanic plates collide, one bends and slides under the other and it forms a trench. When 2 continental plates collide, they squeeze the crust upward into mountain ranges. When a oceanic and continental plate collide, the oceanic plate moves below the continental plate. The oceanic plate melts and forms magma and sinks back into the mantle. The magma can erupt through the continental plate like a volcano.
In sea-floor spreading, molten material rises from the mantle and erupts along___.
mid-ocean ridges
What did scientists in a submersible see when they observed the mid-ocean ridge?;Rocks formed by the rapid hardening of molten material
pillow rock
How did scientists discover that rocks farther away from the mid-ocean ridge were older than those near it?
By determining the age of rock samples obtained by drilling on the sea floor.
The process of ___ continually adds new crust to the ocean floor along both sides of the mid-ocean ridge.
Sea-Floor Spreading
Subduction occurs where the oceanic crust bends down toward the mantle at a
deep-ocean trench
