Plate Motions and Triple Junction Stability Lab

Insure that you understand the difference between relative and absolute plate motions.  For this lab we will deal with the relative motions between pairs of plates.

You may do this lab individually or in groups.  You will be tested on it during a quiz next week.

• Change program version to geology.
• Open the help file, and read the section on Triple Junctions Computations. It contains analyses of  the Indian Ocean triple junction. and the Gulf of California triple junction.  Note that it describes using geometric and analytic solutions .  You should use the geometric option.
• File, Structural Geology lab,  triple junctions.
• Analyze the following triple junctions. You should do this with the HS3-NUVEL-1A plate model since it has more plates included.  You can verify the motions with a web plate motion calculator.
• The Nazca--Cocos--Pacific triple junction
• The triple junction at S45, W76.
• # Queen Charlotte Triple Junction, in British Columbia, at about N51.  You  can use the Juan de Fuca Plate motion since none of these models includes the Explorer plate.

Plate motion calculators, if you want to check results or use an alternative method.

Deliverables: each triple junction you should discuss:

• Velocity stability diagram. It should be approximately correct; you can estimate the velocities and angles.
• Nature of the triple junction (ridge-ridge-ridge, etc.)
• Is the triple junction stable, and if so, will it be migrating.  If it is not stable, how large a change would be required to make it stable.
• Include a map with the ages of the seafloor, and an elevation map from ETOPO1 to explain the relationships.

Triple junctions used in previous semester

The Philippine--Pacific--Eurasian triple junction SE of Japan. Some scientists think the Eurasian--North American plate boundary is west of its location on the map in MICRODEM (for instance Map of the plates), and that this triple junction is actually Philippine--Pacific--North America. Repeat the calculations for this configuration, and does it make much difference (i.e. what are the relative plate velocities between North America and Eurasia in this region?) Repeat the calculations for the APKIMA plate model.

Last revision 9/29/2015