Geology

The peninsula of Baja California is separated from mainland Mexico by the Gulf of California—a long, tapered extension of the Pacific Ocean. The Gulf of California is also known as the Sea of Cortez, and both terms are casually interchanged.  

Geologic History

GEOLOGIC HISTORY

The Gulf of California rides along the boundary of the North American plate and the Pacific plate, and the interaction between these two plates as well as continental drift formed the gulf. Baja California is positioned over the well-known San Andreas fault, a rift known for its restlessness responsible for recurrent earthquakes and geologic transformations. Geologists conjecture that the Baja California peninsula was formed 6-10 million years ago as the fault shifted northward. As such, the peninsula split from mainland Mexico. This timeline also makes the gulf one of the fasted basins formed in history as even large basins such as the Atlantic Ocean can rift for 30-80 million years before beginning the sea-floor spreading process.

Because Baja California lies on a divergent plate boundary where heated earth materials rise up and push plates apart from a spreading center, Baja California will eventually be disconnected from the continent. Fault activity continues today, and the gulf existing between Baja and Mexico is growing.

Baja Geology

BAJA GEOLOGY

Baja California is comprised of five provinces based on geologic landforms.

  1. The broad, flat coastal plains
  2. The fault block mountains and alleviated valleys of the basin and ranges
  3. The isolated coastal mountains
  4. The tilted granitic fault blocks of the main mountain ranges
  5. The plateaus of the volcanic tablelands

Mountain ranges stretch along the peninsula from the northwest to the southeast. The mountains originated as faults, evidence of past tectonic activity such as the east Pacific rise that sheared the peninsula from the North American plate. Currently, visitors will find gentler mountain slopes to the west, and the peninsula’s mountains form a plateau as they stretch southwards.

 

Baja Volcanoes

BAJA VOLCANOES

Tres Vírgenes volcano is a compound of three different stratovolcanoes: El Azufre, El Viejo, and La Vírgen. Tres Vírgenes lies in the central-east region of Baja California and remains the peninsula’s only large volcano complex. The three volcanoes lie on a NE-SW angle and become progressively younger as they reach the southwest. La Vírgen is the youngest volcano in the volcanic triumvirate, while El Viejo is the oldest. With a summit of 1940m and an elevation of 6363 feet, Tres Vírgenes is an impressive sight to see.

Stratovolcanoes—or composite cones—are the most picturesque volcanoes with their steep rise from the gentler lower slopes. The summit generally contains a small crater that does not mar the overall concave shape. Though they are visually stunning, with examples like Mt. Fuji and Mt. St. Helens, they are also the deadliest volcano type due to their pyroclastic flows where volcanic fragments and toxic gases are shot from the volcano at speeds that rival a hurricane.

That being said, Tres Vírgenes has a relatively quiet history that belies its stratovolcano heritage. The last recorded reference to the volcano complex’s most recent eruption can be found in the drawn maps and records of Ferdinand Konščak, a Croatian Jesuit missionary, who referenced an eruption in 1746.