Plate Tectonics – samples of old mid-term questions

 

These questions are for your reference only. I will not provide answers to these questions, but I will be happy to help you with general questions.

 

A. Multiple Choices

 

Alfred Wegener called the single landmass in his reconstruction of drifted continents

a) Laurasia          b) Pangaea           c) Gondwana             d) Atlantis

 

According to the geodynamo model, the Earth’s magnetic field results from

a) rotation of the inner core

b) convection in the outer core

c) convection within the mantle

d) magnetization of crustal rocks

 

Tectonics plates consist of 

a) the crust and the uppermost mantle

b) only large continents

c) the lithosphere and the asthenosphere

d) only oceanic crust

 

Deep earthquakes are usually found in

a) mid-ocean ridges

b) large transform faults

c) subduction zones

d) all above

 

What is the most common mineral in the upper mantle?

a) olivine      b) garnet      c) quartz       d) proviskite

 

The paleomagnetism of oceanic crust is mainly in the form of

a) thermoremanent magnetization (TRM)   

b) chemical remanent magnetization (CRM)      

c) detrital remanent magnetization (DRM)

d) all above

 

B. Short Questions

 

1) List three major lines of evidence used by Wegener to support his hypothesis of continental drift.

 

Label the reflected P and S waves in the figure (hint: Snell’s law).

 

Using sketches to show how the location of the Euler pole can be determined from the transform faults.

 

Why rocks older than ~180 million years are not found from the ocean basins?

 

C. Simple Calculations

 

The Central Andes stand 4000 m above the sea level on average. At the sea level the crustal thickness near is 40 km. Assuming the average crustal and mantle density is 2700 kg/m3 and 3300 kg/m3, respectively.

 

a) Assuming perfect Airy Isostasy, estimate the total crustal thickness of the mountain ranges.

 

b) If erosion take away 2000 m crustal material from the top of the mountain range, what the new isostatic elevation?

 

 

D. Draw and read figures

 

Here is a focal mechanism solution of the recent xxx earthquake from the USGS web site. What is the orientation of the fault plane (strike and dip)? What kind of fault is it? (a “beach ball” focal mechanism solution is provided)

 

Sketch a typical strength envelope of the continental crust and discuss why most earthquakes occur in the upper crust.