Download Mountain Building, Earthquakes, and Sea Floor

Mountain Building, Earthquakes, and Seafloor Landforms

Mountain Building  Terms: 



Ranges  linear association of peaks System  combination of ranges

Mountain Building  Mountains 

form in various ways:

Volcanic  Due

to both convergent and divergent plate boundaries



Differential weathering and erosion  Erosion



of batholiths that are revealed at the surface

Block faulting  Tensional

stress pulls and causes normal faults  The uplifted blocks are horsts  The down dropped blocks are grabens

Mountain Building  Orogeny

 mountain building episodes 



This occurs at convergent plate boundaries You will see deformed sediments present at a current or historical orogeny

Mountain Building  Continent

– Continent Convergence  This happened when the Indian and Eurasian plates collided.  Because of this convergence that continues even today the Himalayans are still “growing”  There are other convergences that produce orogenies but this is the main one

Earthquakes  Earthquakes

are vibrations of the earth, caused by a sudden release of energy, usually as a result of faulting  Magma

movement can also trigger earthquakes  Usually caused by a transform plate boundary

Earthquakes  Aftershocks

are adjustments along a fault after an earthquake, but still are felt as vibrations  This is because of the elastic rebound theory 

When the strength of rocks is exceeded, the rocks will snap back to their former shape

Earthquakes Terms:  Seismology

 the study of earthquakes  Seismograph  instrument which measures earthquakes  Focus  location where the earthquake originates  Epicenter  location on earth’s surface directly above the focus (usually what is mentioned by the media)

Earthquakes  Seismic

Waves

 Body

Waves travel through the Earth  P waves  Primary

waves  These are the fastest, and the first detected  They act as compressional waves

Earthquakes S

waves

 Secondary

waves  These are shear waves/transform waves, they move perpendicular to line of travel  These waves cannot be transmitted through a liquid

Earthquakes  Surface

Waves are waves that travel on the ground  Rayleigh waves (R-waves)  Slower

moving wave  Moves similar to water waves (circular)  Love

waves (L-waves)

 Lateral

motion waves  These waves cause damage to the foundations of many buildings

Earthquakes  Locating  You

the Earthquake

need three locations where P and S waves were measured  With those locations circles can be drawn that have radii equal the distance measured from a time-distance graph

Earthquakes  The

intersection of these three circles is the location of the epicenter  This needs to be done quickly so the population can be warned about other effects of the earthquake

Earthquakes  Effects:  Ground

shaking (most obvious)  Ground failure  Solifluction and liquefaction  Slumping  Landslides  Fire  Tsunamis  seismic sea waves

Earthquakes  Distribution:  80%

occur in the circum-Pacific belt, along convergent plate margins  15% occur in the Mediterranean-Asiatic belt  15% are scattered, some occur in plate interiors  1811-1812

New Madrid, MO  Failed rift valley

Seafloor  The    

 

Ocean Basins

97.2% of Earth’s water is in the Oceans Pacific Ocean Atlantic Ocean Indian Ocean Arctic Ocean Seas are smaller bodies of water  Red Sea  Dead Sea  Caspian Sea

Seafloor  Profile:  



Coast Continental margins  Continental shelf  Continental slope  Continental rise Deep ocean basin

Seafloor  Continental 

Margins

Types:  Active     

Oceanic plate is subducted beneath continental plate (convergent plate boundary) No continental rise is present There is an oceanic trench though Very narrow continental shelf Lots of volcanoes, earthquakes, and mountains

Seafloor  Passive  Occur   

within a plate area

Broad continental shelves Has both continental slope and rise There is an absence of a trench

Seafloor 

Continental shelf  Gentle slope downwards  Varies in width  Ends at the shelf – slope break  Average depth today is 135 m

Seafloor 

Continental slope  Steep decline  Presence of submarine canyons  Sediment is transported by gravity at this point  

This is a location of turbidity currents/graded bedding Deposits from the turbidity currents and other gravity flows accumulate in submarine fans

Seafloor 

Continental rise  Very

gentle slope  Sediments are transported by gravity  This is not present in an active margin  In the passive margins, sediments form series of overlapping fans and develops the rise

Seafloor  Deep Ocean Basin  

Very dark, cold, intense pressure felt here Abyssal plain  Large

flat areas  Sediments have buried the rugged seafloor 

Trenches  Long,

narrow areas  Deepest parts of the ocean; associated with volcanoes 

Oceanic ridges  Volcanic

rocks (basaltic)  Tensional forces/divergent plate boundaries  Ridges are often offset by transform faults