Continued ocean-continent convergence brings continents on opposite plates together as ocean in between closes
Resulting collision of the two continents produces mountains. (e.g. Himalayas, Alps, Appalachians)
Term
Continent on the subducting plate finally reaches the trench:
Definition
The less dense, buoyant continental lithosphere does not subduct, but instead pushes against the adjacent continent on the opposite plate
Term
Alpine Orogeny
Definition
Converging plates resulted in complex faults, overturned folds and crustal shortening
Term
The Appalachian Mountains
Definition
Convergence between eastern North America and Africa ~230 million years ago
Term
Earthquakes
Definition
An earthquake is generated when slippage occurs along a fault plane
Energy is released as seismic waves
Term
Focus
Definition
is the area of fault slippage on the fault plane
Term
Epicenter
Definition
the area on the surface directly above the focus
Term
Elastic Rebound Theory
Definition
Fault plane initially at rest
Term
A major earthquake may be preceded by a series of smaller earthquakes called
Definition
foreshocks
Term
Smaller tremors called aftershocks
Definition
may occur over days to months following the main earthquake
Term
Modified Mercalli Scale:
Definition
Ranges from I – XII – Based on amount of damage
Term
Richter Scale
Definition
– Numeric scale – Based on the amplitude of seismic waves
Term
Moment Magnitude Scale:
Definition
Measures the energy released by earthquake – Considers amount of fault slippage and nature of the bedrock
Term
The energy released by a seismic wave increases by a factor of
Definition
33 for each unit on the Richter scale
Term
San Andreas Fault
Definition
Major strike-slip fault system in California Slippage differs along different segments
Term
Major strike-slip fault system in California
Definition
Marks the transform plate boundary between North American and Pacific Plates
Term
Slippage differs along different segments
Definition
Some segments continuously slip in what is known as fault creep – Other segments slip at regular intervals, generating small earthquakes – Still other segments are tightly locked:
Term
Volcanism
Definition
Volcanic eruptions release enormous amounts of Earth’s internal heat Over 1300 identifiable volcanic cones and mountains exist on Earth:
Term
Over 1300 identifiable volcanic cones and mountains exist on Earth:
Definition
– Fewer than 600 are active today
Term
Locations of volcanic eruptions:
Definition
– Divergent plate boundaries (mid-ocean ridges) – Convergent plate boundaries – Intraplate volcanism associated with mantle plumes and hot spots
Term
Central vent or conduit
Definition
connects volcanic mountain with underlying magma chamber
Term
Crater
Definition
is a circular depression usually formed at the summit
Term
Types of eruptions
Definition
Lava Pyroclastics Steam often vented due to heating of groundwater by underlying magma chamber
Term
Lava
Definition
Magma that erupts on surface
Term
Pyroclastics
Definition
Pulverized rock and clastic materials ejected violently during explosive eruptions
Term
Volcanic eruptions can be
Definition
mild (effusive) or explosive
Term
Factors that determine the type of volcanic eruption:
Definition
Temperature of the magma (hotter are more fluid) – Magma chemistry and viscosity: Dissolved gases:
Term
– Magma chemistry and viscosity:
Definition
Low silica magma (< 52 wt% SiO2) more fluid
Term
Dissolved gases:
Definition
Higher gas content and greater viscosity leads to more explosive eruptions
Term
Effusive Eruptions
Definition
Relatively gentle eruptions
Term
Erupts enormous volumes of basaltic lava:
Definition
– Silica content < 52 wt% – Rich in iron and magnesium
Term
Sites of effusive eruptions
Definition
– Mid-ocean ridges along divergent plate boundaries – Shield volcanoes associated with mantle plumes and hot spots – Plateau (flood) basalts on continents also associated with mantle plumes and hot spots
Term
Effusive Eruptions On Seafloor Due To
Definition
Decompression Melting Beneath Mid-ocean Ridge
Term
Rising mantle encounters
Definition
lower pressures that cause partial melting and generation of basaltic (mafic) magma
Term
Intraplate volcanism
Definition
– Occurs within a tectonic plate – Associated with mantle plumes – Localized volcanic regions in the overriding plate are called hot spots:
Term
Localized volcanic regions in the overriding plate are called hot spots:
Definition
Produces basaltic magma sources in oceanic crust (e.g., Hawaii and Iceland)
Term
Shield Volcanoes
Definition
Constructed from successive flows of basaltic lava: Volcanoes have broad, gentle slopes
Term
Constructed from successive flows of basaltic lava:
Definition
– Low silica content – Low viscosity – Thus fluid and flows easily over great distances
Term
Plateau (Flood) Basalts
Definition
Often associated with mantle plumes and hot spots
Occur when low-viscosity basaltic lava erupts through fractures in crust called
Extensive flows are called
Term
Occur when low-viscosity basaltic lava erupts through fractures in crust called
Definition
fissures
Term
Extensive flows are called
Definition
flood basalts
Term
Extensive flows are called flood basalts
Definition
Fluid nature of the lava allows it to flow great distances (~150 km) from the source – Successive flows can build up to great thicknesses (tens to hundreds of meters thick) and cover large areas (thousands of square km)
Term
Columbia River flood basalts are products of
Definition
basaltic fissure eruptions 17 million years ago
Term
Explosive Eruptions
Definition
Typically occur at subduction zones along convergent plate boundaries
Term
Magma produced by melting of subducted crust and mantle through addition of water
Definition
– Higher silica content (> 56 wt%) – More viscous – Often gas rich
Term
Composite Volcanoes
Definition
Erupt both lavas and pyroclastic material
Term
Caldera
Definition
After violent eruption, the empty magma chamber below the vent no longer able to support its roof
Term
Cinder Cones
Definition
Constructed from ejected lava (mainly cinder-sized) fragments and pyroclastic material
Term
Characteristics of cinder cones:
Definition
–Small size –Steep slope angle –Frequently occur in groups
Term
Volcanoes and Climate
Definition
Explosive eruptions emit huge quantities of gases and ash – Portion of the incoming solar radiation is reflected and filtered out by atmospheric volcanic material – Climatic cooling results
Term
Examples of volcanism causing climatic cooling:
Definition
Mount Tambora, Indonesia – 1815 – Krakatau, Indonesia – 1883 – Mount St. Helens, Washington - 1980 (-0.1o C) – Mount Pinatubo, Philippines - 1991 (-0.5o C)
Term
Which of the following features exhibits the greatest relief?
Definition
. Mountains
Term
hich of the following is NOT characteristic of a craton?
Definition
Only consists of undeformed sedimentary rocks younger than 500 million years
Term
One way by which continents grow is through addition of igneous material along ______
Definition
. Convergent plate boundaries
Term
Which of the following most likely causes a supercontinent to break apart?
Definition
supercontinent prevents heat in the underlying mantle from escaping, thus generating upwelling mantle plumes that break the supercontinent apart.
Term
____________ stress and strain most likely occur along a divergent plate boundary.
Definition
Tensional
Term
Horizontally-layered sedimentary rocks can be folded into arches called _________ and troughs known as ____________.
Definition
Anticlines/synclines
Term
Which of the following is (are) LEAST LIKELY associated with a convergent plate boundary?
Definition
. Tensional stress
Term
Which of the following steps is NOT consistent with the Elastic Rebound Theory for generating an earthquake?
Definition
. A persistent earthquake causes the strain around the locked fault to build up (increase) even more
Term
Which of the following LEAST LIKELY forms in response to compressional stress?
Definition
Rift valley
Term
which of the following types of magma will most likely result in fluid, basaltic lava flows and mild eruptions?
Definition
Low silica and gas-poor magma
Term
Where would composite volcanoes most likely form?
Definition
. Convergent plate boundary
Term
Which of the following is LEAST LIKELY an environmental effect of an explosive volcanic eruption (see Fig. 1.7 in textbook)?
Definition
Net increase in solar radiation at Earth's surface
Term
Cinder cones...
Definition
Are generally small and constructed of pyroclasic material.
