Where it is and what it carries
The Rivera Plate covers about 101,000 square kilometers, or 0.02% of Earth’s surface. It lies in the Pacific Ocean off the coast of the Mexican states of Jalisco and Colima, south of the mouth of the Gulf of California. It is made of young oceanic crust, and no country has land on it.
It is one of the smallest plates in the PB2002 model. Like the Cocos Plate to its southeast, it is a leftover fragment of the old Farallon Plate that once lay off western North America.
What happens at its edges
The Rivera Plate’s longest boundary, 800 km, is with the Pacific Plate. It combines short segments of the East Pacific Rise with the long Rivera Transform fault. The average relative speed along this boundary is about 7 cm/yr.
On its eastern side, the plate converges with the North American Plate at the northern end of the Middle America Trench. This boundary moves slowly, averaging about 2 cm/yr, with speeds that range from about 0.4 cm/yr in the northwest to about 3.6 cm/yr in the southeast. The Rivera Plate sinks beneath the Jalisco Block, a piece of western Mexico bounded by rifts.
The short boundary with the Cocos Plate, about 105 km in the PB2002 model, moves at about 1.3 cm/yr. Its exact location is uncertain, and several different traces have been proposed. Some researchers link it to the Colima Rift, which cuts inland across western Mexico along the eastern edge of the Jalisco Block.
Earthquakes and volcanoes
The dataset lists eight earthquakes of magnitude 6.5 or larger on the plate since 1900, all offshore. The largest were an M6.97 event in 1905 and an M6.9 event in 1997. The most recent was an M6.6 earthquake in 2016.
Bigger earthquakes happen on the overriding plate when the subduction fault slips. The 1932 Jalisco earthquakes and the 1995 Colima-Jalisco earthquake both struck this stretch of coast.
The plate has no volcanoes in the dataset, but its subduction helps feed volcanoes on land. Colima Volcano, one of the most active volcanoes in Mexico, sits above the sinking Rivera and Cocos slabs in the western part of the Trans-Mexican Volcanic Belt.