Chapter 17 and 21
How old is our Earth?
4.5 billion years old.
Which feature is associated with a continental-continental plate boundary?
A mountain range.
Which landform results from divergence of continetal crust?
A rift valley.
What happens when an oceanic plate converges with a continental plate?
A trench and a mountain range with many volcanoes form.
Who came up with the Continental drift?
Alfred Wegener.
Pangaea was an ancient super-continent made up of ________.
All of Earth's continents.
Metallic or silica-rich object, 1 m to 950 km in diameter, that bombarded early Earth, generating heat energy.
Asteroid.
What were the first organisms to live on Earth?
Bacteria.
Oceanic crust is made mostly of ________.
Basalt.
Tectonic plates interact at places called plate ________.
Boundaries.
Name given to the Precambrian shield in North America because much of it is exposed to Canada.
Canadian shield.
Wegener's hypothesis that Earth's continents were joined as a single landmass, called Pangaea, that broke apart about 200 mya and spread out from it's center.
Continental drift.
Changes land:
Convergent Boundary.
Places where tectonic plates come together are called _________.
Convergent boundaries.
Place where two tectonic plates are moving toward each other.
Convergent boundary.
Earth's layers: (inside to outside)
Core, mantle, crust.
Most scientists at the time rejected Wegener's hypothesis of continental drift because he _______.
Couldn't explain how or why the continents moved.
The deepest and most stable part of a continent is called a _________.
Craton
Continental core formed from Archean or Proterozoic micro-continents.
Craton.
Most stable part of plate tectonics _______.
Craton.
Earth's __________ probably formed as a result of the cooling of the uppermost mantle.
Crust
The process by which a planet becomes internally zoned is called __________.
Differentiation
Process in which a planet becomes internally zoned, with the heavy materials sinking toward the center and the lighter materials accumulating near its surface.
Differentiation.
Places where tectonic plates move apart are called _______.
Divergent boundaries.
Forms new land:
Divergent boundary.
Place where two of Earth's tectonic plates are moving apart.
Divergent boundary.
The Mid-Atlantic Ridge is an example of ________.
Divergent boundary.
True/false- The oldest ocean floor rocks are about 3.8 BILLION years old.
False- 180 million.
True/ false- The thickness of ocean floor sediments DECREASES with distance from an ocean ridge.
False- increases.
True/false- AN ISOCHRON is a change is in Earth's magnetic field.
False- magnetic reversal.
True/false- The magnetic patterns on either side of a DEEP-SEA TRENCH are mirror images of each other.
False- mid oceanic ridge
True/false - DEEP-SEA TRENCHES are vast underwater mountain chains
False- ocean ridges.
True/false- The theory of CONTINENTAL DRIFT states that new ocean crust is formed at ocean ridges and destroyed at deep-sea trenches.
False- seafloor spreading.
True/false- Rock samples taken near ocean ridges are OLDER than rock samples taken near deep-sea trenches.
False- younger.
True/false- As new seafloor is carried away from an ocean ridge, it becomes more dense, HEATS UP, EXPANDS, AND BECOMES LESS DENCE than the material beneath it.
False-cools, contract, more dense.
Less-dense material such as crust has a tendency to _________ on more-dense material such as the mantle.
Float
Continental to Continental:
Forms mountains.
Was constructed from data gathered from continental basalt flows.
Geomagnetic time scale.
The common crustal rock _________ is mainly composed of feldspar, quartz, and mica, which are minerals with densities.
Granite
Rock that makes up crust:
Granite.
What area has lots of volcanoes?
Hadian area.
When Earth formed, the dense element _________ was concentrated in Earth's core.
Iron
What is Earth's core made up of:
Iron and nickle
Minerals containing this act like small compass needles and record the orientation of Earth's magnetic field at the time of their formation.
Iron.
This type of line connects points on a map that have the same age.
Isochron
Imaginary line on a map that shows points of the same age.
Isochron.
Ancient continent formed during the Proterozoic that is the core of modern-day North America.
Laurentia.
Earth's ____ has changed over time.
Magnetic field.
When Earth's magnetic field changes polarity between normal and reversed.
Magnetic reversal.
Device that can detect small changes in magnetic fields.
Magnetometer.
Devices used to map the ocean floor that detects small changes in the magnetic fields.
Magnetometer.
Denser minerals concentrated below Earth's surface and formed the rocks that make up Earth's _________.
Mantle
Where does convection occur?
Mantle.
Early mapmakers thought continents might have moved based on their observations of _______.
Matching coastlines
A small fragment of an orbiting body that has fallen to Earth, generating heat.
Meteorite.
A small fragment of granite-rich crust formed during the Archean.
Micro-continent.
What happens along a divergent boundary?
New ocean crust forms.
Each cycle of spreading and magma intrusion along an ocean ridge results in the formation of this.
New ocean crust.
A field with the same orientation as today's field is said to have _________.
Normal polarity.
A difference in density causes the __________ to be lower in elevation than the less-dense granitic continental crust.
Oceanic crust
Divergent boundary example:
Oceanic ridge.
Where are most divergent boundaries found?
On the seafloor.
Study of Earth's magnetic record using data gathered from iron-bearing minerals in rocks that have recorded the orientation of Earth's magnetic field at the time of their formation.
Paleomagnetism.
What is the history of reversals?
Paleotology.
Ancient landmass made up of all the continents that began to break apart about 200 mya.
Pangaea.
Which theory states that Earth's crust and rigid upper mantle move in different directions and at different rates over Earth's surface?
Plate tectonics
The top of craton exposed at Earth's surface.
Precambrian shield.
A field that is opposite the present field has _________.
Reversed polarity.
Tectonic process associated with convection currents in Earth's mantle that occurs when the weight of an elevated ridge pushes an oceanic plate toward a subduction zone.
Ridge push.
Long, narrow depression that forms when continental crust begins to seperate at a divergent boundary.
Rift valley.
The hypothesis that new ocean crust is formed at mid-ocean ridges and destroyed at deep-sea trenches.
Seafloor spreading.
Tectonic process associated with convection currents in Earth's mantle that occurs as the weight of the subducting plate pulls the trailing lithosphere into a subduction zone.
Slab pull.
Sediment-covered slabs of Earth's earliest crust were recycled into the mantle at __________ zones.
Subduction
What forms when two oceanic plates converge?
Subduction zones.
Below the surface.-
Subduction.
Process by which one tectonic plate slips beneath another tectonic plate.
Subduction.
Huge pieces of Earth's crust that cover its surface and fit together at their edges.
Tectonic plate.
At which tectonic plate boundary do plates slide horizontally past each other?
Transform boundary.
Place where two tectonic plates slide horizontally past each other.
Transform boundary.
True/false - Maps made from sonar and magnetometer data led to the discovery of OCEAN RIDGES AND DEEP-SEA TRENCHES.
True
True/false - SONAR uses sound waves to measure water depth
True
True/false - Earthquake activity and volcanism are common along OCEAN RIDGES.
True.
True/false- The Precambrian lasted for about 4 billion years.
True.
True/false- The theory of seafloor spreading explains that Earth's continents move because they RIDE ATOP OCEAN CRUST AS IT MOVES AWAY FROM OCEAN RIDGES.
True.
True/false- the study of the magnetic record preserved in Earth's rocks is called PALEOMAGNETISM.
True.
Early Earth's crustal fragments, or micro-continents, formed on Earth's surface by ________.
Volcanic activity
Very stable and common mineral that scientists often use to age-date old rocks.
Zircon
Above the surface-
Abduction.
No change to land:
Transform or slip fault.
