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.
