Seafloor Spreading
Where is the youngest rock on the seafloor found?
Near mid-ocean ridges.
How old is the Earth?
4.6 billion years
What is the thinnest layer of the Earth?
The crust.
At which type of plate boundaries do earthquakes occur?
All of them.
What do we call it when part of the crust "slips" along a fault?
An earthquake
What causes the movement of Earth's tectonic plates?
Convection currents in the mantle
What is the largest time unit?
An eon.
Why does the crust float on top of the mantle?
The crust is less dense than the mantle.
A mid-ocean ridge is an example of what kind of plate boundary?
A divergent plate boundary.
At which type of plate boundaries do volcanoes form?
Convergent and divergent
Why does oceanic crust subduct underneath continental crust when they meet?
Oceanic crust is more dense than continental crust.
What is used to organize Earth's history?
A geologic time scale.
Why is the inner core of the Earth solid?
The pressure is extremely high.
Mountains form at which kind of plate boundary?
A convergent boundary.
What are the two types of waves produced by an earthquake that travel through Earth's interior?
P-waves (primary) and s-waves (secondary)
How did the discovery of seafloor spreading support Wegener's hypothesis of continental drift?
It provided a mechanism.
Why are fossils useful when studying geologic time?
How have scientists developed a model of the interior of the Earth?
They study the refraction of seismic waves.
Crust is neither created nor destroyed at which type of plate boundary?
A transform boundary.
Describe how magma is generated at a subduction zone.
Water from the ocean saturates the crustal rock.
Friction from the subducting plate melts rock in the mantle.
This heat rises and warms the saturated crustal rock above it enough for it to melt.
If a mid-ocean ridge has a rate of plate separation of 5.0 cm/year, how long will it take for the separation to increase by 5.0 meters?
100 years.
What kind of events have caused the transitions from the paleozoic era to the mesozoic era, and the mesozoic era to the cenozoic era?
Mass extinction events.
Which layer of the Earth is made of liquid iron and nickel?
The outer core.
Describe the cycling of matter in a convection current.
Warmer matter rises and cooler matter sinks.
Describe how magma is created at a spreading center.
As two plates spread apart, the pressure on the crustal rock is lowered, lowering its melting point.
Friction from the moving plates warms the depressurized rock enough for it to melt.