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8th Grade Science > Geology > Flashcards

Flashcards in Geology Deck (111):

What is the purpose of a model?

to have a visual aid that is a replica of the original object to better make observations, especially if the original object is too big or too small to observe properly


What is the difference between a scaled model & a model that is nt scaled?

a scaled model is proportional to the original object, but a non-scaled model isn't


What is the difference between a scaled down model & a scaled up model? (& example)

a scaled down {reduced} model is smaller than the original object (ex: globe vs earth) & a scaled up {enlarged} model is larger than the original object (ex: a cell vs a model of a cell)


What are Earth's layers determined by?

composition (what each layer is made of) & physical properties (i.e. temperature, density, ability to flow, state of matter, etc.)


Crust: % of Earth's mass, thickness, & composition

less than 1%; continental - Avg = 30 km, oceanic - 5-8km; continental - granite, oceanic - basalt


Mantle: % of Earth's mass, thickness, & composition

67%; 2,900 km; Iron (Fe) & Magnesium (Mg)


Core (inner/outer): % of Earth's mass, thickness, & composition

33%; 6,858 km (diameter); Iron (Fe) & Nickel (Ni)


What is the crust?

• the outermost layer
• the thinnest layer


What are the 2 types of crust?

oceanic & continental


What are the differences between oceanic crust & continental crust?

• continental crust is thicker than oceanic crust
• oceanic crust is more dense than continental crust


What is the MOHO?

the boundary between the mantle & the crust


What is the Lithosphere?

the topmost solid part of the Earth that is broken into plates that move; the crust & top part of mantle


What is the Mantle?

• it is extremely thick & contains most of the Earth's mass


Where can mantle rock be seen?

on the ocean floor at underwater volcanoes


What is the composition of the mantle?

mostly iron & magnesium


The rock in the mantle can ___ ___ like a thick liquid.

flow slowly


What is the property called in which a solid can flow slowly like a thick liquid?



What is the Oute Core made of?

liquid iron & nickel


What is the Inner Core?

• innermost layer of the Earth


What is the inner core made of?

solid iron & nickel


What are some physical properties of the inner core?

very high temperature, pressure, & density


How would the plasticity of the mantle influence the movement of the crust?

it would cause the crust & tectonic plates to shift, which could create earthquakes


What is the Continental Drift Theory?

the theory that 200 million years ago, the Earth only had one giant continent, from which today's continents broke apart & drifted into their current locations


Who proposed the Continental Drift Theory?

Alfred Wegener


What was this "supercontinent" called? What does it mean?

Pangaea ~ "all earth"


What are 3 pieces of evidence to support the Continental Drift Theory?

1) Fossils of the same plant & animal species that couldn't have crossed an ocean have been found on both sides of the Atlantic Ocean.
2) Similar types of rock & the same climate conditions can be found on several continents.
3) When all of the continental pieces are put in their original placement, the glacial grooves (grooves in the ground left by glaciers in the direction they traveled) match up.


What is the theory of Plate Tectonics?

Plate Tectonics is the theory that the Earth's lithosphere is divided into tectonic plates that move around on top of the asthenosphere.


What is Sea Floor Spreading?

at mid ocean ridges, molten rock is forced up from inside the earth at the ridge, forming into new crust. this new crust is gradually pushed away as new molten rock comes up.


Where would the oldest crust in the ocean be found?

closer to land, further away from the mid ocean ridge


How does a Divergent Boundary occur?

occur as 2 tectonic plates move away from each other, resulting in an upwelling of material from the mantle to create a new sea floor


Is oceanic crust created or destroyed at a divergent boundary?



How much oceanic crust is formed along the Mid-Atlantic Ridge?

1 inch / year


What is a Convergent Boundary?

where plates are moved together


What is a Subduction Zone?

where one (more dense) plate is pushed down under another (less dense) plate at a convergent boundary


Is oceanic crust created or destroyed at a convergent boundary?



What are the 3 types of convergent boundaries?

1. Continental-Oceanic
2. Oceanic-Oceanic
3. Continental-Continental


What is the tallest mountain range on earth? Due to what type of boundary? What 2 plates create this mountain range? How much does it increase by each year?

Himalayan Mountains (Mt. Everest); Continental-continental convergent boundary; Eurasian Plate & Indian-Australian Plate; increases about 2cm / year


What are some features & effects found along convergent boundaries?

Mountain ranges (c-c), volcanic arcs (o-c, o-o), trenches (o-c, o-o), & earthquakes


What is a Transform Fault Boundary?

where plates grind past each other without the production or destruction of the earth's crust


What is a strike-slip fault?

where 2 plates collide & try to slip past each other


Why are earthquakes found along transform fault boundaries?

b/c as the plates are trying to move past each other, friction is causing the plates to lock, & that strain increases until they fracture. the sudden release of energy is an earthquake


How do tectonic plates interact with each other to change continents?

at the boundaries (divergent, convergent, & transform), the plates interact w/ each other & create volcanoes, mountain ranges, & fractures in the earth's surface. the pulling or pushing of plates can change the location & shape of continents


What can hot spots make?



What is a Hot Spot?

a place on the Earth's surface that is directly above a column of rising magma called a mantle plume


What is the Ring of Fire?

the plate boundaries surrounding the Pacific Ocean have so many volcanoes that these boundaries together are called the Ring of Fire


What is Folding?

the bending of rock layers due to stress in the Earth's crust


What is an Anticline?

a bowl-shaped fold in sedimentary rock layers

(upside down "u")
(an upward fold)


What is a Syncline?

a trough-shaped fold in sedimentary rock layers

(a right-side-up "u")
(a downward fold)


What is a Monocline?

a fold in sedimentary rock layers in which the layers are horizontal on both sides of the fold


What is a Fault?

a break in the Earth's crust along which blocks of the crust slide relative to one another due to tectonic forces


What is a Normal Fault?

a fault in which the hanging wall moves down relative to the footwall


When do Normal Faults usually occur?

when rocks are pulled apart due to tension


What is a Reverse Fault?

a fault in which the hanging wall moves up relative to the footwall


When do Reverse Faults usually occur?

when rocks are pushed together by compression


What is a Strike-Slip Fault?

a fault in which the 2 fault blocks (whose fractures are vertical or nearly vertical) move past each other horizontally


What is Mountain Building?

the process in which the tectonic plates continuously move around & bump into each other, causing mountains to form


What are Folded Mountains?

mountains that form when rock layers are squeezed together & pushed upward

(when 2 tectonic plates collide)


What are Fault-Block Mountains?

mountains that form when faults or cracks in the Earth's crust force some blocks of rock up or down


What are Volcanic Mountains?

mountains that form when molten rock erupts onto the Earth's surface


When will the next supercontinent be formed?

in 50 to 200 million years


What will the next supercontinent be called?



How and where will the continents come together to form Amasia?

North & South America will come together, and Asia will join with the Americas, at the North Pole


Are earthquakes & volcanoes scattered randomly over the surface of the earth or are they concentrated in definite zones?

They are more concentrated at plate boundaries, especially at the Ring of Fire. They are, for the most part, located near the edges of continents.


What relationship exists between the locations of earthquakes & of volcanoes?

They are usually found close by each other or in the same location, and they can mostly be found along plate boundaries.


What is an Ash Cloud?

the cloud of ash that forms in the air after some volcanic eruptions


What is a Conduit?

a passage through which magma (molten rock) flows in a volcano


What is Lava?

molten rock; it usually comes out of erupting volcanoes


What is a Magma Chamber?

the area that contains magma (molten rock) deep within the Earth's crust


What is a Vent?

an opening in the Earth's surface through which volcanic materials erupt


What is a Side Vent?

a vent in the side of a volcano


What is a Shield Volcano?

a broad, dome-shaped volcano with a wide base, gentle slopes, & a large bowl-shaped opening at the top. it covers a large area


Why do shield volcanoes have gentle slopes?

b/c they are made of many layers of a kind of volcanic rock (basalt) that flows easily when melted. when the basalt flows out of the vent, it forms thin layers sloping away from the crater


When a shield volcano erupts, what happens?

lava quietly flows from the vent


What is a Cinder Cone?

a steep conical hill that is formed above a vent, with steep sides & a steep cone, & is often smaller than a shield volcano, & wears away easily


What are cinders (in a cinder cone)?

bits of volcanic rock (andesite & sometimes basalt) that make up cinder cones


When a cinder cone erupts, what happens?

cinders & rock particles are blown out of the vent & harden in the air. when they land, they pile up around the crater to form a steep cone


What is a Composite Cone?

a large, cone-shaped volcano formed by alternating layers of cinders & lava, with steep sides


What keeps composite cones from wearing away fast?

the layers of hardened lava


When a composite cone erupts, what happens?

a violent eruption sends up volcanic bombs, cinders, & ash. a quiet volcanic flow follows the eruption. alternating layers continue forming the mountain


Why are composite cones often bigger than cinder cones?

b/c the hardened lava keeps them from wearing away fast


After a shield volcano erupts, it usually is...

a little higher b/c most of the lava runs down the sides of the volcano


Mt. Mcklinley in Alaska is 1 of the world's highest volcanoes. From its size, we can tell that it is not what type of volcano?

it isn't a cinder cone


What is an Earthquake?

a disturbance in the earth's crust wen one section moves past another


What is Amplitude?

The size of a wave generated by an earthquake


What is Magnitude?

a measure of the energy released by an earthquake


What is Seismology?

the science that studies earthquakes & their causes


What causes an earthquake?

volcanic or magmatic activity, other sudden stress changes in the earth; when tectonic plates move past each other causing stress


What is an earthquake?

the resulting ground-shaking & radiated seismic energy caused by a sudden slip on a fault


What is the Focus?

the point inside the earth where an eathquake begins


What is the Epicenter?

the point on the earth's surface above the focus; the point on the surface of the earth above which an actual earthquake has taken place


What is a Seismometer?

an instrument used to detect & record earthquakes


What is a Seismogram?

a recording produced by a seismograph, showing the time of arrival of different earthquake waves & their intensities


What does P Wave stand for?

Primary Wave


What is a P Wave?

a type of seismic wave that compresses & expands the ground; the first wave to arrive at an earthquake


What can P Waves travel through?

both solids & liquids


What does S Wave stand for?

Secondary Wave


What is a S Wave?

a type of seismic wave that moves the ground up & down or side to side


What can S Waves travel through?

only solids


What do Surface Waves do?

move along the earth's surface; produce motion in the upper crust


What are 2 types of Surface Waves, and how do they move?

L Waves - move up & down
Raleigh Waves - motion can be all around


What's a difference between Surface Waves & S & P Waves?

Surface Waves travel more slowly & are more destructive


What is Triangulation?

a technique that uses 3 data points - and thus, 3 seismographs - to plot a location


What do scientists use triangulation for?

to determine the epicenter of an earthquake


How are earthquakes measured?

the Richter Scale & the Mercalli Intensity Scale


What is the Richter Scale based on?

the amplitude (size) of the waves


How does the Mercalli Intensity Scale measure an earthquake's intensity?

by analyzing the effects of the earthquake / the damage it leaves behind


What is a Tsunami?

a series of large waves & rushing water


How & where is a Tsunami formed?

formed by a fault underwater; occurs in a large body of water


What is a warning sign that a Tsunami is coming?

the shoreline recedes (water is sucked back into the ocean)


What happens to S Waves as they hit the outer core of the earth? Why?

the S Waves stop/disappear. the outer core is made of liquid


Why might the P Waves bend as they enter & exit the outer core?

they are changing from traveling in a solid to traveling in a liquid & vice versa, and the speed also changes (P waves are faster in a solid)