Gulf of California Triple Junction

Triple junction motion rules

  Predicted sea floor ages  (MÜLLER and others) at the mouth of the Gulf of California. Spreading patterns run north-south, with some east-west transforms.
Earthquakes at the mouth of the Gulf of California.
  • Normal faults
  • Thrust faults
  • Strike slip faults
Volcanoes at the mouth of the Gulf of California.

Red triangles are stratovolcanoes; all others small blue diamonds.

Plate boundaries in red; note that the three boundaries do not come together to form a triple junction. This is a reflection on the digitized boundaries rather than nature.

Smith & Sandwell predicted topography at the mouth of the Gulf of California.

Plate boundaries and volcanoes overlaid.

Note the arcs to the east of the ridge south of the triple junction, showing rapid increases in the spreading rate moving southward, and proximity to the Euler pole.

 Plate motions from the NUVEL model at the location of the triple junction. MICRODEM can produce this with   Rotate continents button and Triple junction option.
Relative plate motions indicated between the three plate pairs. This must be done graphically on the output.

Although this is done on the map background, it is not a map, but a diagram in velocity space. Note in particular that the NA and CO plates have reversed positions, a consequence of the subduction of CO under NA. CO moves northeast (under NA).

Motions of the three plate boundaries indicated.
  • PA-CO ridge's velocity line is close to the perpendicular bisector of the PA-CO velocity vector.
  • NA-CO trench is fixed to NA (earthquakes and volcanoes are all on the overriding plate, and isostasy predicts the continental NA plate will override oceanic CO). Its trend is parallel to the trench.
  • NA-PA strike slip boundary's velocity line (earthquake mechanisms) is along the NA-PA velocity vector, and is parallel to the plate boundary.

This must be done graphically on the output.

The triple junction is stable because the three velocity lines for the boundaries intersect in a point. The triple junction does not move relative to North America, but moves relative to the two other plates.

Spreading velocity along the Cocos-Pacific plate boundary (East Pacific Rise) and   Rotate continents button and Two plate motions option.

NUVEL model velocities calculated at three points, in red. The green lines show the relative motion between the plates, with the black line pointing to the spots where the calculations are valid at the tails of the vectors for each platemotion.

Note the southward increase in velocity, from 65 mm/yr (full rate) to 92 mm/yr in the middle and 110 mm/yr at the Galapagos triple junction. These figures are calculated by scaling the computed green relative vectors to one of the red vectors or looking at the scale bar the program can compute.

Last revision 9/20/2015