Chapter 11 & 12 Flashcards
What is continental drift?
the idea that the continents move around the Earth.
Who discovered the continental drift
Alfred Wegener
What was Wegener’s hypothesis?
He hypothesized that the continents were once connected.
Was Wegener right?
YESSSSS
What is Pangea?
(Greek for “all land”). An ancient, huge landmass composed of earlier forms of todays continents; an ancient super continent.
What is a supercontinent?
Its the very large landmass that separated to make the continents.
What is Wegeners evidence for continental drift?
- Coal bed match each other in eastern U.S and southern Europe.
- Plant fossils found in South America, Africa, India, Australia, and Antarctica.
- Matching reptile and mammal fossils found in South America and Africa.
- Evidence of glaciers in warm, dry areas that show that they used to be closer to the South Pole.
Was Wegener’s hypothesis good?
YESSSSSSSSSS and was based on observations.
Why did scientists initially reject the continental drift?
There was no evidence to explain HOW the continents moved.
What is a mid-ocean ridge
a long chain of undersea mountains.
Why was the ocean floor mapped for the first time?
It was for the United States Navy to locate enemy submarines hiding on the bottom of shallow areas.
Who is Harry Hess?
He is an American geophysicist and naval officer who did a lot of the ocean mapping of the ocean floor.
What was Hess’s idea?
A new ocean floor is created at deep mid-ocean ridges. This pushes apart the continents that meet at that mid-ocean ridges.
What is sea-floor spreading?
a hypothesis that new sea floor is created at mid-ocean ridges and that, in the process, the continents are pushed apart from each other.
What was one key piece of evidence for Hess’s hypothesis?
Magnetic Reversal Patterns
What is magnetic reversal patterns?
They are patterns formed in new rock formations by the Earth’s magnetic field. The patterns harden as the rock cools.
What did scientists notice about magnetic reversal patterns?
They noticed that the magnetic patterns matched on either side of the ridge. The oldest rocks were furthest from the ridge.
What are lithospheric plates?
large pieces of Earth’s lithosphere that move over the asthenosphere.
What are two types of lithospheric plates?
The oceanic and continental plates.
What are oceanic plates made of and formed?
It is made of basalt and formed the ocean floor.
What are continental plates made of and how are they different from oceanic plates?
It is made of andesite and granite and is less dense than the oceanic plate.
What drives the lithospheric plates on the surface?
Convection Cells in the lower mantle of the Earth.
What happens in the mid-ocean ridge when lithospheric plates move?
Convection cell in the mantle moves the lithospheic plate.
Basaltic lava goes through the mid-ocean ridge and joins the lithospheric plate where it makes it bigger.
What is subduction?
a process that involves a lithospheric plate sinking into the mantle.
Describe the parts of the convection cell moving the lithospheric plates?
Page 252. - Hot lower mantle rises up
- The lava comes up through the mid-ocean ridge and adds on to the plate and cools.
- The mantle material is moving and carrying the lithospheric plate like a passenger
- SUBDUCTION, the mantle material cools and the plate starts to sink.
What is mantle plume?
heated lower mantle rock that rises toward the lithosphere because it is less dense than surrounding mantle rock.
How can a mantle plume cause and island?
When there is a big volcanic eruption it can form and island.
What are three type of boundaries between lithospheric plates?
Divergent convergent, and transform fault boundary
What is a divergent boundary?
a lithospheric plate boundary where two plates move apart.
What is a convergent boundary?
a lithospheric plate where two plates move into each other.
What is a transform fault boundary?
A lithospheric boundary where two plates slide by each other.
What kind of boundaries are mid-ocean ridges and where are they found?
Divergent boundaries and found over the rising part of a mantle convection cell.
What is it called when divergent boundaries are found on continents?
Rift Valley
What is a deep-ocean trench
a valley in the ocean created when one lithospheric plate subducts under another.
What happens when continents collide?
Vast mountain ranges are formed. EX: HIMALAYAS
How can we find transform fault boundaries?
- Zig Zag Patterns
- A lot of Earthquakes
What kind of boundaries do earthquakes happen?
All three!
What kind of boundaries do volcanoes happen at?
Convergent and Divergent
What are slickensides?
Rocks surfaces moving against each other.
What is a foreshock?
a small burst of shaking that occurs before a large earthquake.
What is a aftershock?
a small tremor that follows an earthquake.
What happens during an earthquake?
There is a lot of shaking in the ground.
What is liquefaction?
If the ground becomes saturated with water, the shaking soil might act like a liquid in a process called liquefaction.
What is a earthquake?
the movement of Earth’s crust resulting from the release of built-up potential energy between two stuck lithospheric plates.
What is a focus?
the point below Earth’s surface where a rock breaks or slips and causes am earthquake.
What is a fault?
a region on Earth’s surface is broken and where movement occurs.
What is an epicenter?
a point on Earth’s surface right above the focus of an earthquake.
What are the three conditions for the stick-slip motion?
- Touch
- Force
- Friction
What is a seismograph?
an instrument that measures and records seismic waves.
What are body waves?
seismic waves that travel through the interior of Earth.
What are surface waves?
seismic waves that reach and travel along Earth’s surface.
What is the Richter Scale?
a scale that ranks earthquakes according to the size of the seismic waves. Every number you move up on this scale, the wave amplitude gets 10x higher.
What is the Moment Magnitude Scale?
- scale that measures the total energy released from earthquakes
- It is similar to the Richter Scale until 5.
- For very large earthquakes we use this.
What is the Modified Mercalli Scale?
a scale that rates the damage experienced by buildings, the ground, and people during an earthquake.
What is a volcano?
an erupting vent through which molten rock and other materials reach Earth’s surface, or a mountain built from the products of an eruption.
What is magma?
underground melted rock.
What is a magma chamber?
a location where magma collects inside Earth.
What is lava?
magma that has reached and cooled on Earth’s surface.
What is a caldera?
the bowl-shaped depression formed by the collapse of a volcano after it has erupted.
What is a lava lake?
a pool of lava that has formed in a caldera.
What is an active volcano?
a volcano that is erupting or that has erupted recently.
What is a dormant volcano?
a volcano that is not erupting now, but that may erupt in the future.
What is an extinct volcano?
a volcano that no longer erupts and is in the process of eroding.
What is a volcanic neck?
solid remains of magma that filled the conduit of an extinct volcano. The neck is exposed as the volcano erodes.
Where does magma come from?
Solid mantle rock
What is quartz?
A mineral made from silica.
What is a shield volcano?
a flat and wide volcano that has low-silica magma and lava with low or high levels of dissolved gas.
What is a cinder cone?
a volcano that has low-silica magma and lava with high levels of dissolved gas; these volcanoes produce “fire fountain” eruptions.
What is a composite volcano?
a tall, explosive, cone-shaped volcano formed by layers of silica-rich lava and ash.
What is a pyroclastic flow?
a destructive cloud of volcanic material that moves quickly down the side of a volcano after an explosive eruption.
What is a lava bomb?
large pieces of glowing lava thrown from an explosive eruption.
What is a lahar?
a mudflow that results from a volcanic eruption.
What is the Ring of Fire?
a region of Earth’s plate boundaries where oceanic crust is subducting under other plates; active volcanoes and earthquakes are common here.
What is a volcanic island arc?
a series of volcanoes formed at a subduction zone.
What is a hot spot?
the top of a mantle plume
What is a volcanic island arc?
a series of volcanoes formed as a lithospheric plate moves over the hot spot
What are the 7 major lithospheric plates?
Pacific, American, Nazca, African, Eurasian, Indo-Australian, and Antarctic Plates.
What is the Ring of Fire and what does it have tot do with plate tectonics?
An area around the Pacific Ocean with the most volcanoes and earthquakes. Volcanoes and Earthquakes happen most often at plate boundaries.
