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Convergent Plate Boundaries Describe what a convergent plate boundary is… Plates collide; Crust is destroyed (surface area is lost) or recycled
Identify differences that occur when at least one of the plates involved is oceanic. Subduction occurs when one of the plates involved is oceanic; the oceanic plate is forced underneath
Describe how this interaction alters the surface of the Earth. Crust is recycled/destroyed in these areas; formations like folded mountains, faults form & earthquakes occur;
when subduction happens, volcanoes & ocean trenches form
Example of Ocean-­‐Continent Evidence Supporting This is a Convergent Boundary: Volcanic mountains, Folds, Underwater trenches off the coast, MegaCollision: thrust earthquakes (that could lead to tsunamis), Igneous rock
Andes Mountains
Example of Ocean-­‐Continent Evidence Supporting This is a Convergent Boundary: Volcanic mountains, Folds, Underwater trenches off the coast, MegaCollision: thrust earthquakes (that could lead to tsunamis), Igneous rock
Cascade Mountain Range
Example of Ocean-­‐Ocean Evidence Supporting This is a Convergent Boundary: Volcanic mountains that form beginning under the ocean so an Island Arc
Collision: Any of the following
is present, Folds, Underwater trenches off the coast, Mega-thrust
work: Mariana Islands, Japan,
earthquakes (that could lead to tsunamis), Igneous rock Philippines, Aleutian Islands Example of Continent-­‐Continent Evidence Supporting This is a Convergent Boundary: Tall, non-volcanic mountains, Folds, Earthquakes (only in the Himalayas –
Collision: not in the Allegheny Mountains as that is no longer an active convergent
Himalayas or
boundary)
Allegheny/Appalachian Mountains
Divergent Plate Boundaries Describe what a divergent plate boundary is… Plates pull apart/divide and magma/lava fills in the gap in between, which creates new crust (new igneous rock)
Identify the differences that occur when a divergent boundary occurs on land as opposed to underwater. The same process occurs, but underwater it is referred to as a “ridge” and on land it is called a “rift.”
Describe how this interaction alters the surface of the Earth. New rock/land forms (which compensates for the destruction along convergent boundaries); small earthquakes
and volcanoes alter the surface of the Earth.
Example Underwater: Evidence Supporting This in a Divergent Boundary: Atlantic Ocean, along the MidSmall volcanic mountains (referred to as a “ridge”), new igneous
Atlantic Ridge (runs along the center rock/land forms, not-very-strong earthquakes, faults, the Atlantic Ocean
of the Atlantic Ocean)
widens ~1-2 inches per year
Example on Land: Evidence Supporting This in a Divergent Boundary: African Rift Valley (sometimes called Small volcanic mountains (referred to as a “rift”), new igneous rock/land
“The Great Rift Valley”)
forms, not-very-strong earthquakes, faults Example #3: Evidence Supporting This in a Divergent Boundary: Iceland
Small volcanic mountains (referred to as a “rift”), new igneous rock/land
forms (Iceland grows ~1-2 inches each year), not-very-strong earthquakes,
faults, geysers, hot springs Transform Plate Boundaries Describe what a transform plate boundary is… Plates slide past each other; there is no vertical (up and down) motion along transform boundaries)
Describe how this interaction alters the surface of the Earth. Earthquakes alter the surface of the Earth as they move/shift material/features found on the surface.
Example #1: Evidence Supporting This in a Transform Boundary: Port-au-Prince, Haiti
Earthquakes, Faults, No igneous rock (sedimentary & metamorphic rock is
found there), objects moving horizontally as plates slide, No mountains, No
volcanoes – Few geologic features
Example #2: Evidence Supporting This in a Transform Boundary: San Andreas Fault, California
Earthquakes, Faults, No igneous rock (sedimentary & metamorphic rock is
found there), objects moving horizontally as plates slide, No mountains, No
volcanoes – Few geologic features Hotspot Describe what a hotspot is… Magma rises from beneath the Earth’s surface through a weak spot in the crust (usually not along a plate
boundary); Plate moves above the hotspot (hotspot remains fixed).
Describe how a hotspot alters the surface of the Earth. Creates a chain of extinct volcanoes as the plate moves over the hotspot (this helps to identify the direction and
speed of plate motion over time); Volcanoes forms at hotspots which can alter Earth’s surface & creates new
land/igneous rock.
Example #1: Evidence Supporting This in a Hotspot: Hawaii
Trail of extinct volcanoes leading to the current, active on (on the “big
island”), Volcanoes (forming a new island off the southeast coast of Hawaii),
Not-very-strong earthquakes (as the magma rumbles below the crust), New
igneous rock forming
Example #2: Evidence Supporting This in a Hotspot: Yellowstone
Trail of extinct volcanoes leading to the current volcanic activity, Geysers
(“Old Faithful”), Igneous rock, Not-very-strong earthquakes
Analysis 1. Using the information you just compiled, identify the four ways volcanoes form on Earth. When
(1) Divergent Boundaries
Subduction
(2) Convergent Boundaries (when two oceanic plates collide)
Occurs
(3) Convergent Boundaries (when an oceanic plate collides into a
continental one)
(4) Hotspots 2. Along which kind of plate boundary is there NO chance that a mountain or mountain range will form? Transform Boundary 3. You may see new volcanic islands forming because of two different reasons… which geologic forces that we’ve been studying would cause them to be created? (1) Hotspots (if they occur underwater), like the island chain that is Hawaii
(2) Convergent Boundaries (when two oceanic plates collide), like the island arcs that are Japan,
the Philippines, Mariana Islands and the Aleutian Islands
4. There is one event that is a piece of evidence that you could observe anywhere the plates are moving compared to one another. What is it? Earthquakes