ch19 flashcards

Question 1

continental drift

Answer 1

The hypothesis proposed by Alfred Wegener that the continents have moved across Earth’s surface over geological time, once forming a single supercontinent (Pangea) before breaking apart

Question 2

plate tectonics

Answer 2

The unifying theory that Earth’s lithosphere is broken into rigid plates that move over the asthenosphere, interacting at divergent, convergent, and transform boundaries

Question 3

fit of continents

Answer 3

The observation that coastlines, such as those of South America and Africa, appear to match up when placed together, supporting the idea of once-connected continents

Question 4

rock and structure similarities

Answer 4

Identical or closely matched rock types, mountain belts, and geologic structures found on continents now separated by oceans, providing evidence of past continental connections

Question 5

fossils

Answer 5

Remains of the same plant and animal species found on continents now widely separated, indicating these landmasses were once joined and shared similar ecosystems

Question 6

paleoclimate

Answer 6

Ancient climate evidence (e.g., glacial deposits in currently tropical regions) that suggests continents have shifted positions over time, changing their climate belts

Question 7

polar wandering

Answer 7

The apparent movement of the Earth’s magnetic poles over time, recorded in rocks and indicating that continents have moved rather than the poles themselves shifting significantly

Question 8

paleomagnetic reversals

Answer 8

Periodic switches in the direction of Earth’s magnetic field preserved in igneous rocks, providing a record of spreading at mid-ocean ridges and supporting seafloor spreading

Question 9

age and thickness of seafloor sediments

Answer 9

Sediments become older and thicker with increasing distance from mid-ocean ridges, confirming new crust forms at ridges and moves outward

Question 10

divergent plate boundary

Answer 10

A plate margin where plates move apart, often creating mid-ocean ridges (oceanic divergence) or rift valleys on land (continental divergence)

Question 11

oceanic boundary (divergent)

Answer 11

A mid-ocean ridge where new oceanic crust forms as basaltic magma rises and solidifies, leading to seafloor spreading

Question 12

continental boundary (divergent)

Answer 12

A continental rift zone where the crust stretches and thins, potentially evolving into a new ocean basin if rifting continues

Question 13

convergent plate boundary

Answer 13

A plate margin where two plates move toward each other, causing one plate to subduct or mountains to form, depending on the plate types involved

Question 14

ocean-ocean boundary (convergent)

Answer 14

A subduction zone where one oceanic plate sinks beneath another, often creating island arcs and deep trenches

Question 15

ocean-continent boundary (convergent)

Answer 15

A subduction zone where an oceanic plate is forced under a continental plate, generating volcanic mountain arcs and trenches along the coast

Question 16

continent-continent boundary (convergent)

Answer 16

A collision zone where two continental plates converge, forming large, uplifted mountain ranges due to their similar buoyancy (e.g., the Himalayas)

Question 17

accretionary wedge

Answer 17

A mass of sediment and rock scraped off the subducting plate and piled against the overriding plate at a convergent margin

Question 18

forearc basin

Answer 18

A sediment-filled depression located between an accretionary wedge and a volcanic arc in a convergent margin setting

Question 19

magmatic arc (volcanic arc)

Answer 19

A chain of volcanoes formed above a subduction zone where the subducting plate’s fluids lower the melting point of the overlying mantle, generating magma

Question 20

transform plate boundary

Answer 20

A plate margin where two plates slide horizontally past each other along a transform fault, often causing earthquakes

Question 21

hot spot

Answer 21

A stationary mantle plume of hot material rising from deep within the Earth, creating volcanic activity and island chains as plates move over it

Question 22

exotic terranes

Answer 22

Fragments of crustal material with distinct geologic histories that are accreted onto a continent, forming new crustal additions along convergent boundaries

Question 23

Pangea

Answer 23

A supercontinent that existed during the late Paleozoic and early Mesozoic eras, comprising all major continental landmasses before breaking apart into Laurasia and Gondwana

Question 24

Laurasia

Answer 24

The northern portion of Pangea that included present-day North America, Europe, and Asia (excluding India)

Question 25

Gondwana

Answer 25

The southern portion of Pangea that included present-day South America, Africa, Antarctica, Australia, and the Indian subcontinent

Question 26

Tethys Sea

Answer 26

An ancient ocean that separated Laurasia and Gondwana before the closing of the ocean basin and the formation of the modern Mediterranean and related seas

Question 27

Atlantic Ocean

Answer 27

An ocean basin that formed as Pangea split apart, with the opening of the Atlantic marking the start of modern continental configurations

Question 28

convection (in mantle)

Answer 28

The circulation of material in the mantle, driven by heat from Earth’s interior, which is a fundamental process powering plate motion

Question 29

island arc

Answer 29

A curved chain of volcanic islands that form above an ocean-ocean subduction zone

Question 30

mantle plume

Answer 30

A localized column of hot, rising mantle material that can create volcanic activity at the surface, forming hot spots

Question 31

plate

Answer 31

A rigid segment of the Earth’s lithosphere that moves over the asthenosphere, interacting with neighboring plates at boundaries

Question 32

rift valley

Answer 32

A linear-shaped lowland created by the stretching and fracturing of the Earth’s crust at divergent plate boundaries on continents

Question 33

seafloor spreading

Answer 33

The process by which new oceanic crust is generated at mid-ocean ridges and moves away symmetrically, supporting continental drift and plate tectonics

Question 34

subduction

Answer 34

The process where one tectonic plate descends into the mantle beneath another plate, often associated with volcanism and trench formation

Question 35

transform fault

Answer 35

A strike-slip fault at a plate boundary where two plates grind past each other, causing earthquakes but not destroying or creating new crust