Assignment 1.2 Exam 1

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 and duration of the magnetic polarity event

Order the steps of continental volcanic arc formation.

1. A subduction trench forms where the subducting plate bends downwards into the mantle 2. an accretionary prism begins to form 3. magma, created by flux melting of the mantle, rises through the continental lithosphere 4. lava erupts onto the surface, forming volcanoes

Order the steps in continental rift formation.

1. lithospheric mantle begins to stretch horizontally and thin vertically. 2. the crust fractures, and faults develop 3. large fault blocks or crust slide down into the widening rift 4. magma erupts as lava, creating volcanoes along and near the center of the rift.

Order the steps that lead to seafloor spreading.

1. the asthenosphere beneath diverging plates rises and melts 2. a magma chamber forms beneath the ridge axis 3. magma rises to the surface and erupts via submarine volcanoes 4. newly formed crust is moved laterally away from the ridge

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.

Identify statements true of Pangaea.

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

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 and moved by the creation of new crust and subduction of old crust