24 Questions
What is the primary characteristic of transform plate boundaries?
Parallel strike-slip faulting
What is the orientation of transform fault zones relative to the ridge axis?
Perpendicular
Where do transform plate boundaries occur?
In both oceanic and continental lithosphere
What is the cause of deep pull-apart basins in transform plate boundaries?
Fault bending and overlapping
What is the typical location of earthquake activity in transform plate boundaries?
Restricted to the transform portion of the fracture zone
What is the characteristic of the San Andreas Fault system?
A transform plate boundary
What is the term for a zone of volcanism that forms a chain of seamounts?
Hotspot
What is the relationship between plates and hotspots?
Volcanism occurs beneath a moving plate
What is the primary mechanism by which oceanic lithosphere is destroyed and recycled into the asthenosphere?
Subduction
What is the characteristic of the subducted plate in a subduction zone?
It is always composed of oceanic lithosphere
What is the term for the area where the process of subduction occurs?
Subduction zone
What is the result of the repetition of the process of sea floor spreading and magnetic polarity reversals?
The creation of oceanic crust with bands of alternating normal and reversed magnetism
What is the average thickness of the subducted plate in a subduction zone?
100 km
What is the term for the plate that is being forced downward into the underlying asthenosphere in a subduction zone?
Downgoing slab
What is the characteristic of the crust produced during a period of normal magnetic polarity?
It is split into two and spreads away from the ridge axis
What type of plate boundary is characterized by subduction zones?
Destructive plate boundary
What is the primary source of stress in the subducted lithosphere that generates earthquakes?
The interaction between the subducted plate and the surrounding mantle
What is the name of the zone that marks the path of the subducted plate as it descends into the asthenosphere?
Inclined seismic zone
Where did the largest magnitude earthquake in the past century occur?
All of the above
What was the consequence of the 2004 Sumatra earthquake?
A devastating tsunami that killed some 300,000 people
What is the process by which the subducted slab eventually meets its fate?
By melting and recycling into the mantle
What is the term for the region where the subducted plate interacts with the surrounding mantle?
Zone of initial melting
What is the result of the interaction between the subducted plate and the overlying mantle?
All of the above
What is the term for the layer of the Earth's mantle that the subducted plate descends into?
Asthenosphere
Study Notes
Transform Plate Boundaries
- Transform plate boundaries are intraplate features that are generally oriented perpendicular to the ridge axis.
- They are characterized by active strike-slip fault systems.
- Examples of continental transforms include the San Andreas Fault system in California and the Alpine Fault system in New Zealand.
Fracture Zones
- Fracture zones are intensely faulted, fractured oceanic crust that lies between offset ridge segments.
- Earthquake activity is largely restricted to the transform portion of fracture zones.
Hotspots
- Hotspots occur beneath both oceanic and continental lithosphere.
- Examples include Hawaii and Yellowstone National Park, Wyoming.
- Linear seamount chains, such as the Hawaiian Islands, are surface expressions of hotspots.
Subduction Zones
- Subduction occurs when the leading edge of a denser lithospheric plate is forced downward into the underlying asthenosphere.
- The downgoing plate is called the subducted plate or downgoing slab, and the less dense plate is called the overriding plate.
- The area where this process occurs is a subduction zone.
- Subduction is the major process by which oceanic lithosphere is destroyed and recycled into the asthenosphere.
Oceanic Lithosphere
- The age of oceanic crust increases systematically away from the ridge in opposite directions.
- Crust produced during a period of time characterized by normal magnetic polarity should split in two and spread away from the ridge axis as new crust forms during the subsequent period of reversed magnetic polarity.
- Repetition of this splitting process produces oceanic crust with bands of alternating normal and reversed magnetism whose age increases systematically away from the ridge.
This quiz covers the features and characteristics of transform plate boundaries, including their orientation, faulting, and earthquake activity. It also explores their occurrence in both oceanic and continental lithosphere.
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