Chapters 4-9 Flashcards
Weathering
the disintegration and decomposition of material at or near the surface
Mass Wasting
the transfer of rock material downslope under the influence of gravity
Erosion
the incorporation and transportation of material by a mobile agent, usually water, wind, or ice
Mechanical Weathering
Breaking of rocks into smaller pieces Processes of mechanical weathering: -Frost wedging -Unloading -Biological activity
Chemical Weathering
Alters the internal structures of minerals by removing or adding elements
Most important agent is water
Soil
a combination of mineral matter, water, and air – that portion of the regolith (rock and mineral fragments) that supports the growth of plants
angle of repose
Unconsolidated granular particles assume a stable slope called the angle of repose
Stable slope angle is different for various materials
Oversteepened slopes are unstable
Liquefaction
a special type of earthflow sometimes associated with earthquakes
Creep
Slow movement of soil and regolith downhill
Causes fences and utility poles to tilt
Soilfluction
Slow movement in areas underlain by permafrost
Upper (active) soil layer becomes saturated and slowly flows over a frozen surface below
Hydrologic Cycle
Precipitation Evaporation Infiltration Runoff Transpiration
Drainage Basin
Land Area that contributes water to a river system
Gradient
From head (source) to mouth
Profile is a smooth curve
Gradient decreases from the head to the mouth.
Stream’s Load
Transported Material:
Dissolved load
Suspended load
Bed load
Delta
exist in ocean or lakes
Levee
form parallel to the stream channel
Valleys
Characteristics of wide valleys Floodplain Features often include Meanders Cutoffs Oxbow lakes
Sinkholes
Causes dissolving groundwater.
Belt of Soil Moisture
The upper subdivision of the zone of aeration limited above by the land surface and below by the intermediate belt; this zone contains plant roots and water available for plant growth. Also known as belt of soil moisture;
Aquitard
An impermeable layer of material
Aquifer
a permeable layer of material
Zone of Saturation
All pore spaces in the material are filled with water
Water within the pores is groundwater
Geysers
Intermittent hot springs
Water turns to steam and erupts
Dripstone
Compose driptsone: calcite deposited as dripping water evaporates.
Stalactites
Hanging from the ceiling.
Stalagmites
Growing upward from the floor.
Karst Topography
Formed by dissolving rock at, or near, Earth’s surface
Common features:
-Sinkholes – surface depressions
-Sinkholes form by dissolving bedrock and cavern collapse
-Caves and caverns
Area lacks good surface drainage
Glaciers
a thick mass of ice that forms over land from the compaction and recrystallization of snow and shows evidence of past or present flow
Types of Glaciers
Valley, or alpine glaciers – form in mountainous areas
Ice sheets, or continental glaciers
-Large scale
-e.g., Over Greenland and Antarctica
Other types:
-Ice caps and piedmont glaciers (Iceland)
Zone of Wastage
The area where there is a net loss due to melting
Zone of accumulation
The area where a glacier forms.
Glacial Drift
All sediments of glacial origin
Types of glacial drift
-Till – material that is deposited directly by ice
-Stratified drift – sediment deposited by meltwater
Moraine
layers or ridges of till
Types of Moraines
Lateral
Medial (Till from two glaciers)
End
Ground (as glacier recedes)
Indirect effects of Ice Age glaciers
Migration of animals and plants
Rebounding upward of the crust
Worldwide change in sea level
Climatic changes
Milankovitch hypothesis
Shape (eccentricity) of Earth’s orbit varies Angle of Earth’s axis (obliquity) changes (Milder winters and cooler summers) Axis wobbles (precession)
Asthenosphere
Exists beneath the lithosphere
Hotter and weaker than lithosphere
Allows for motion of lithosphere
Divergent plate boundaries (constructive margins)
Two plates move apart
Mantle material upwells to create new seafloor
Ocean ridges and seafloor spreading
-Oceanic ridges develop along well-developed boundaries
-Along ridges, seafloor spreading creates new seafloor
Divergent boundaries are located
along oceanic ridges
Convergent plate boundaries (destructive margins)
Plates collide, an ocean trench forms and lithosphere is subducted into the mantle
Mid Ocean Range
Convergent
Oceanic-continental convergence
Denser oceanic slab sinks into the asthenosphere
Pockets of magma develop and rise
Continental volcanic arc forms
Examples include the Andes, Cascades, and the Sierra-Nevadan system
Transform Fault Boundaries
Plates slide past one another
No new crust is created or destroyed
Transform Faults
Most join two segments of a mid-ocean ridge
Aid the movement of oceanic crustal material
Hot Spots and Mantle Plumes
Caused by rising plumes of mantle material
Volcanoes can form over them (Hawaiian Island chain)
Mantle plumes
Long-lived structures
Some originate at great depth, perhaps at the mantle-core boundary
Slab-pull and ridge-push model
Descending oceanic crust pulls the plate
Elevated ridge system pushes the plate
Mantle Drag
Resists Subduction
Earthquake Waves
Surface waves:
- Complex motion
- Slowest velocity of all waves
Body Waves- Primary Waves: -Push-pull (compressional) motion -Travel through solids, liquids, and gases -Greatest velocity of all earthquake waves Secondary (S) waves: -“Shake” motion -Travel only through solids -Slower velocity than P waves
Wind Wave vs. Tsunami
Same wave height
Different wave length and wave period.
Crust
Thin, rocky outer layer
Varies in thickness
-Roughly 7 km (5 miles) in oceanic regions
-Continental crust averages 35–40 km (22–25 miles)
-Exceeds 70 km (40 miles) in some mountainous regions
Continental Crust
Upper crust composed of granitic rocks
Lower crust is more akin to basalt
Average density is about 2.7 g/cm3
Up to 4 billion years old
Oceanic Crust
Basaltic composition
Density about 3.0 g/cm3
Younger (180 million years or less) than the continental crust
Mantle
Below crust to a depth of 2900 kilometers (1800 miles)
Composition of the uppermost mantle is the igneous rock peridotite (changes at greater depths)
Outer Core
Below mantle
A sphere having a radius of 3486 km (2161 miles)
Composed of an iron-nickel alloy
Average density of nearly 11 g/cm3
Inner Core
Sphere with a radius of 1216 km (754 miles)
Behaves like a solid
Lithosphere
Crust and uppermost mantle (about 100 km thick)
Cool, rigid, solid
Asthenosphere
Beneath the lithosphere
Upper mantle
To a depth of about 660 kilometers
Soft, weak layer that is easily deformed
Mesosphere (Or Lower Mantle)
660–2900 km
More rigid layer
Rocks are very hot and capable of gradual flow
Factors Affecting Viscosity
Temperature (hotter magmas are less viscous)
Composition (silica content):
-High silica – high viscosity (e.g., rhyolitic lava)
-Low silica – more fluid (e.g., basaltic lava)
Dissolved gases (volatiles):
-Mainly water vapor and carbon dioxide
-Gases expand near the surface
Dissolved gases (volatiles)
Provide the force to extrude lava
Violence of an eruption is related to how easily gases escape from magma
-Easy escape from fluid magma
-Viscous magma produces a more violent eruption
Parts of a Volcano
Conduit, or pipe, carries gas-rich magma to the surface
Vent, the surface opening (connected to the magma chamber via a pipe)
Crater
-Steep-walled depression at the summit
-Caldera (a summit depression greater than 1 km diameter)
Shield Volcano
Broad, slightly domed
Primarily made of basaltic (fluid) lava
Generally large size
e.g., Mauna Loa in Hawaii
Cinder Cone
Built from ejected lava fragments
Steep slope angle
Rather small size
Frequently occur in groups
Composite cone (or stratovolcano)
Most are adjacent to the Pacific Ocean (e.g., Mt. Rainier)
Large size
Interbedded lavas and pyroclastics
Most violent type of activity
Lahar
Volcanic mudflow
Viscosity of Volcanoes
Shield- Low Viscosity
Stratovolcano- High Viscosity
