Oceanography Chapter 3 Quiz

What are plates?

rigid, rocky outer surface of the earth

What are tectonics?

to build or destroy

What are tectonic plates?

The processes by which the rocky plates of the planet move and interact with each other

What is the internal structure of the earth like?

It is divided into 4 layers

1. lithospheric plates

2. mantle/hot dense rock

3. outer core/liquid iron

4. inner core/solid iron

What are lithospheric plates?

large pieces of Earth's lithosphere that move over the asthenosphere

What are the two types of lithospheric plates?

oceanic and continental

What are oceanic lithospheric plates?

thin, heavy, mostly lava flow

what are continental lithospheric plates?

thick, light, mostly granite

What is the asthenosphere?

a weak, plastic upper mantle that sits right below the lithospheric plate and is the more fluid layer of the upper mantle

What are the three types of plate boundaries?

1. diverging plate boundaries

2. converging plate boundaries

3. transform plate boundaries

What happens during diverging plate boundaries?

plates pull apart from each other with stretching and thinning. they have high heat flow and create new crust

What are key landforms of diverging plate boundaries?

mid-oceanic ridges, volcanic mountain ranges, axial valley (1000’s miles long and 1-2 miles tall)

What happens during converging plate boundaries?

where plates collide, has subduction zone and also destroys crusts

What are subduction zones?

collision between oceanic and continental lithosphere

What are key landforms of subduction zones?

trenches and volcanic arcs

What happens during transform plate boundaries?

plates slide side by side where crusts are neither destroyed nor created

What are key landforms of transform plate boundaries?

faults

What are the driving force of the movement of tectonic plates?

thermal convection/convection currents

What happens during a thermal convection?

Hot rock/less dense mantle pushes up at the ridges and the plates there spread apart. the hot rock/magma fills in these ‘cracks’ and creates new ocean floor. During this, cold rocks/ dense upper mantle sinks down, replacing the hot rocks that rise in response to this.

What are some geologic activities at plate margins?

volcanism, earthquakes, and rock deformation

Why is the shape of continents evidence of pangea?

the margins of some continents look like they could fit together

Who proposed the idea that the margins of some continents looked like they could fit together?

Alfred wegner

How were fossils evidence to pangea?

The distribution of fossils across the southern continent were identical to one another

how were volcanoes evidence of pangea?

nonrandom occurrence of volcanic activity/ large-scale, symmetrical volcanic chains were formed when the supercontinent began to break apart, creating the Atlantic Ocean

how were earthquakes evidence of pangea?

nonrandom occurrence of earthquakes where they were shallow at diverging margins but deep at converging margins.

how were hot spots (beneath volc) evidence of pangea?

stationary upwellings of heat away from plate margins. As plates move, the volcanoes are carried away from the hot spot. only volcanoes near the hot spot are active. they can determine direction and speed of the plate motion

how is the age of seafloor rocks evidence of pangea?

it confirms the process of seafloor spreading, explaing how supercontinents broke apart

Where are the youngest rocks found on the seafloor?

they are found at the mid oceanic ridges

Where are the oldest rocks found on the seafloor?

they are found farthest from the ridges

What is paleomagnetism?

the study of Earth's ancient magnetic field as recorded in rocks and sediments

How is paleomagnetism evidence of pangea?

earth has a strong magnetic field. Iron rich volcanic rocks record earth’s magnetic field at the time they form

What do paleomagnetic records show?

• paleomagnetic records show bands of alternating polarity

• symmetrical about the mid oceanic ridges

How does seafloor paleomagnetic records happen?

lava forming at the ridges picks up the current magnetism, then gets pushed out of the way as newer lava forms

• records of the growth and spreading of the seafloor is recorded

• the alternating polarity represents complete reversal of earths magnetic field

What happened to eaerths magnetic field due to paleomagnetism?

it caused the complete reversal of earths magnetic field

What are continental paleomagnetic records?

the location of magnetic poles on seperate continents appear to wander with time. if the poles havent moved significantly, then the continents did.

What are some plate tectonics in the pacific northwest?

1. cascadia subduction zone

2. cascades volcanic arc

3. juan de fuca and gorda mid ocean ridges

4. blanco and medocino fracture zones

What is the importance of plate tectonics in the PNW?

the PNW experiences powerful convergence, a process of plates moving into each other

What are Cascadia subduction zones?

a massive, ~600-mile-long fault off the Pacific Northwest coast where the oceanic Juan de Fuca plate dives beneath the North American continental plate, creating a zone of potential megathrust earthquakes

What are Cascades volcanic arc?

the result of eastward subduction of the Juan de Fuca plate

What are Juan de Fuca & Gorda mid ocean ridges?

segments of a mid-ocean ridge system off the Pacific Northwest coast of North America, where the Pacific Plate is pulling away from the Juan de Fuca Plate and the Gorda Plate. This seafloor spreading creates new oceanic crust through volcanic activity

What are Blanco & Mendocino fracture zones?

transform faults in the Pacific Ocean off the coast of California and Oregon, marking boundaries between tectonic plates. These long, linear features are scars on the ocean floor created by mid-ocean ridges being offset due to transform fault activity.

Plate tectonics in the PNW are what?

• “exotic terranes”

• islands carried by the plates

  • attached to the north america continent