Geology Chapter 2

A global map of seismicity shows seismic trends indicating the location of

plate boundaries.

Which of the following variables could influence the width of marine magnetic anomalies on the floor of the ocean?

rate at which the plates are moving away from the mid-ocean ridge duration of the magnetic polarity event

Order the steps that lead to seafloor spreading.

the asthenosphere beneath diverging plates rises and melts. a magma chamber forms beneath the ridge axis. Magma rises to the surface and erupts via submarine volcanoes. newly formed crust is moved laterally away from the ridge.

Order the steps in continental rift formation.

the lithospheric mantle begins to stretch horizontally and thin vertically. the crust fractures, and faults develop. large fault blocks of crust slide down into the widening rift. magma erupts as lava, creating volcanoes along and near the center of the rift.

Identify statements true of Pangaea.

A.Rates of seafloor spreading in the Atlantic Ocean are compatible with what is known about the breakup of Pangaea. B.The regional-scale folds visible in the Appalachian Mountains are remnants of Pangaea's formation. C.Pangaea was one of several supercontinents that have formed and broken up during Earth's history

As the map below shows, the oldest seafloor is generally less than 200 million years old. Why?

All oceanic lithosphere eventually gets subducted beneath the continents by the time it is 200 million years old.

The asthenosphere is actually a part of the ________ of the Earth.

Mantle

The composition of the core of the Earth is thought to be ________.

Solid iron-nickel alloy

Order the steps of volcanic island arc formation.

a subduction trench forms where the subducting plate bends downward into the mantle. an accretionary prism begins to form. Magma, created by flux melting of the mantle, rides through the continental lithosphere. Lava erupts onto the surface, forming volcanoes.

Seafloor spreading is driven by volcanic activity that occurs

along mid-ocean ridges.

According to the theory of plate tectonics, the plates are:

discrete pieces of lithosphere which move with respect to one another. moved by the creation of new crust and subduction of old crust.