Plate Tectonic Boundaries
Earth Science
Geology 007
Types of plate boundaries
transform
divergent
convergent
Divergent Plate Boundaries
continental rift
incipient
ocean basin
mid-ocean
ridge
Divergent Plate Boundary
Central rift valley
Shallow earthquakes
Volcanoes
African continental rift
and incipient ocean
basins
African Volcanoes
Kilimanjaro
African rift valley - Lake Turkana
Global system of mid-ocean ridge
divergent plate boundaries
Seafloor Age - Mid-Atlantic Ridge
Mid-ocean ridge is visible where it crosses Iceland
Rifting and volcanism
in Iceland
Central Rift Valley - Iceland
13
Convergent Plate Boundaries
Wadati-Benioff Zone - region of earthquake activity at a subduction zone
shallow
intermediate
deep
subduction
What
is the orientation
Seismicity
- South
America of subduction?
uctio
subd
n
Cocas
sub
duc
tio
n
Caribbean
Nazca
on
ucti
subd
sub
n
Caribbean
uctio
subd
duc
tio
n
What is the orientation of subduction?
Cocas
Nazca
on
ucti
subd
Convergent Boundary: Ocean - Continent
Convergent Plate Boundary
Ocean - Continent
Shallow - intermediate - deep
earthquakes
Wet mantle volcanism - stratovolcanoes
Continental compression - high mountain
range with volcanoes
Seismicity - South America
Volcán Tungurahua, Ecuador
Cascades Volcanic Range
Mt. Rainier
Mt. St. Helens
Mt. Hood
Mt. Adams
Mt. Rainier, Seattle, Washington
Convergent Boundary: Ocean - Ocean
Convergent Plate Boundary
Ocean - Ocean
Shallow - intermediate - deep
earthquakes
Wet mantle volcanism - stratovolcanoes
Volcanic island arc
Mt. Redoubt - Aleutian Islands, Alaska
Volcanic Island
Arcs - East
Seismicity
- Southern
AsiaAsia and Indonesia
cti
on
bd
u
su
subd
su
bd
u
cti
on
n
uctio
Volcanism - Central America / Caribbean
Seismicity
Volcanoes of the Lesser Antilles
Soufriere Hills, Montserrat
34
Seismicity - Southern Asia
Convergent Boundary: Continent - Continent
Convergent Plate Boundary
Continent - Continent
Shallow earthquakes
No volcanism
High mountain range and plateau due to
crustal thickening
Alps
Zagros Mtns.
Western Himalaya
Seismicity - Europe
Tibetan Plateau
Himalayan Mtns.
Mt. Everest
Seismicity - Southern Asia
Himalaya Mountains
Makalu
Mt. Everest
Everest
Transform Plate Boundary
Tectonic plates sideswipe each other
Shallow earthquakes
horizontal displacement of the crust
over great distances
Transform boundary
displaced stream
San Andreas Fault
Transform boundary
Hot Spots
• Localized regions of high heat flow in the
mantle.
• Generates melting in the overlying crust.
• Remain fixed for between 20 million and 100
million years while plate rides over.
• Many aseismic ridges produced by hot spots.
Hot Spots
Hawai’ian Ridge and
Emperor Seamount
hotspot trail
Emperor Seamounts
Plate motion
Hawai’ian Ridge
Hawai’ian Islands
Hot Spot
Causes of Plate Movement
• Ridge Push
– plates are moving down slope due to gravity, from
high elevation at ridges to low elevation in
trenches.
• Slab Pull
– Subducting slab sinking into mantle pulls the rest
of the plate behind it.
• Both!