Faults and Landforms
In a normal fault, this wall moves downward.
The hanging wall
This type of stress pulls on Earth’s crust, stretching rock and making it thinner.
Tension
The point on Earth’s surface directly above the earthquake’s focus.
The epicenter
At divergent boundaries, volcanoes usually form here.
Along mid-ocean ridges
Thin, runny magma with low silica causes this type of eruption.
A quiet eruption
Reverse faults are most likely found at this type of plate boundary.
Convergent plate boundaries
This type of stress squeezes rock until it bends or breaks, often forming mountains.
Compression
This device records seismic waves and produces a seismogram.
A seismograph (or seismometer)
This type of boundary forms volcanic island arcs.
Convergent boundaries where oceanic plates subduct
Magma with high silica leads to eruptions that are described as this.
Explosive
A strike-slip fault forms when walls of rock do this.
Slide past each other in opposite horizontal directions
This type of stress pushes rock in opposite directions, causing it to bend or break.
Shearing
These two seismic waves (the fastest ones) arrive before surface waves.
P waves and S waves
Hot spot volcanoes form above these rising areas of hot mantle material.
Mantle plumes
These two tools can detect signs that a volcano is swelling and preparing to erupt.
Seismographs and tiltmeters
A valley that forms when a block drops down between two normal faults is called a _______.
Rift valley
All three types of stress can create these two major surface features.
Folds and faults
What happens to seismic waves when they pass from one material to another?
They change speed and direction.
A volcano that forms alternating layers of lava and ash is known as a _______.
Composite volcano (stratovolcano)
This 1883 eruption produced a tsunami and cooled global temperatures for years.
Krakatau (Krakatoa)
Describe how fault-block mountains are formed through tension.
Tension pulls plates apart, causing multiple normal faults; the hanging-wall block drops down to form a valley while the footwall blocks remain higher, becoming fault-block mountains.
Explain how stress at plate boundaries can “change Earth’s surface over millions of years.”
Stress deforms rock through tension, compression, and shearing, creating mountains, valleys, rift zones, and fault-block mountains that reshape Earth’s surface over long periods of time.
Explain how scientists locate an earthquake’s epicenter using data from multiple stations.
Scientists compare arrival times of P and S waves at several seismograph stations; circles are drawn around each station based on distance, and the point where all circles meet is the epicenter.
Explain how a subducting plate leads to volcanic formation at convergent boundaries.
Water from the sinking plate enters the mantle, lowering the melting point and forming magma; the magma rises and erupts to form volcanoes.
Explain how increased sulfur dioxide emissions help predict volcanic eruptions.
Higher SO₂ levels indicate rising magma; escaping gas shows pressure is building, suggesting an eruption is likely.