Unit 4.3: Internal forces Flashcards
What is a land form?
single unit that forms part of the general topography
Define geomorphology
The study of landforms. Their origin, processes, and evolution of features.
what are 2 processes that control and affect landforms? what will they produce?
- internal forces: geothermal energy like volcanoes and tectonic activity. they will produce initial landforms.
- external forces: running water, glaciers, gravity, and wind. they will produce secondary landforms.
what is a volcano?
conical or dome-shaped initial landform built by the emission of lava and contained gases from a constricted vent.
where is the most volcanic activity found?
along plate boundaries
what is the ring of fire?
concentration of volcanoes on the periphery of the Pacific Ocean from the Philippines around to the west coast of South America.
what are the 3 classifications for volcanoes based on the possibility of eruption?
- active volcano: has erupted in recorded history and has the potential to do it again.
- dormant volcano: not erupted in recorded history but shows eruption of past eruption
- extinct volcano: no sign of life, evidence of long-term erosion
what are 4 types of volcanoes?
- stratovolcano: large and cone shaped, composed of alternating layers of lava and pyroclasts. they do not move which creates the steep-sided, symmetrical appearance. they are the most dangerous
- shield: broad, gently sloped. formed from layers of basaltic lava that is very fluid. eruptions are not too explosive. Hawaiian islands are this type.
- cinder cone: small, cone shaped composed primarily of pyroclasts. formed during brief periods of explosive activity
- lava dome: dome shaped. formed when thick lava cannot flow easily so it piles up around a vent and solidifies into a dome structure.
What are the different types of lava?
- Mafic: low viscosity and flows in stream over large distances. low silica content 50% or less. 1000o-1200oC
- Intermediate: medium silica and viscosity content 50-70%. 800o-1000oC
- Felsic: high silica content, 70% or more, and viscosity. does not flow for far distances. 650o-800oC
- pyroclasts: anything that is emitted from volcano eruptions
what does it mean when lava has higher viscosity?
more resistant to flowing
what are the different types of pyroclasts?
- volcanic ash: droplets of lava that solidify in atmosphere and rain down
- pumice: lightweight, pores rick with atleast 50% air content, formed form intermediate and felsic lava. cools in air or underwater.
- lapilli: marble-golfball sized fragments of lava ejected from a volcano that is cooled and hardened as It moves in air. can reach the size of a mini-van
- volcanic block: fragments of rock that is ejected from volcano cone during eruption.
What is a lahar?
volcanic mudflow caused when hot ash melts snow and ice. it is not hot but it does move very fast and that is what makes it dangerous.
- hot lahar: triggered by an eruption
- cold lahar: when warm season rainfall mobilizes previously deposited ash
What are some features formed after lava eruption?
- columnar jointing: geometric jointing pattern that develops as lava cools and hardens, and cracks develop in the rock
- large igneous provinces: accumulations of basaltic lava that covers large spatial areas
- caldera: depression forms when volcano walls collapse after eruption. can be large and fill with water.
What does the volcanic explosivity index?
measures size of volcanic eruption. based on amount of material ejected. it is both subjective and based off of quantitative data
what is folding?
wrinkles/bending of crust resulting from deformation and compressional forces.
what are some features of folding?
- anticlines: downfolds or folds with arch-like ridges
- synclines: downfolds or folds in crust with a u-shaped dip
what is faulting?
when the crust breaks from not being able to fold anymore.
what is a block landform?
faulting creates blocks of crust that move vertically relative to each other.
what are the different types of faults?
normal, reverse, strike-slip
what is a normal fault?
created by tensional forces (pulled apart). one block lifts over other.
multiple sets in one area will create:
- Horsts: uplifted block between 2 normal faults
- grabens: dropped blocks between 2 normal faults
what is a reverse fault?
created by compressional forces. rock is compressed into smaller space and there is a shortening of the crust resulting in one block riding over the other.
fault scarp: the cliff face
what is a strike-slip fault?
2 blocks move laterally along fault plane horizontally.
what is an earthquake?
when rocks bend or brake and they release a built up tension/ energy that was stored in the rock.
what is the difference between the focus and the epicentre of the earthquake?
focus: origin of earthquake
epicentre: point directly above focus on earths surface
what are the different seismic waves emitted by energy of earthquakes?
- P waves: compressional waves that travel in the interior of the earth (primary)
- S waves: secondary, interior waves
- R waves: surface, compressional waves that travel through crust creating vertical movement
- L waves: shear, surface waves that travel through crust and create horizontal movement
what is the modified mercalli intensity scale?
intensity of earthquake based on damage caused, ranked using Roman numerals. they rank location rather than individual earthquake.
what is earthquake magnitude based on?
ground shaking and energy released
what is a hotspot?
non-boundary volcanic activity. results from mantle plume that is stationary. magma moves up this vertocle column.
