Volcanoes of east-central Baja California
Encyclopedia
The Volcanoes of east-central Baja California are located on the Baja California Peninsula
near the Gulf of California
, in the state of Baja California Sur
, in Mexico
.
, facing the Gulf of California
, near Santa Rosalia, Baja California Sur
. The outer rim of the caldera
is defined by dark-colored rocks made out of very fluid lava. A dome of rock in the center of the caldera is a resurgent dome. A resurgent dome
is formed as the floor of the caldera is heaved upward by the movement of magma below ground. The lavas surrounding the caldera date to about 1 million years ago.
, a line of three connected volcanoes, collectively known by that name, are west of La Reforma Caldera. La Vírgen, in the southwest, El Azufre in the center, and El Viejo in the northeast. The volcanoes get larger and younger from northeast to southwest. As recently as 6,500 years ago, La Vírgen experienced a Plinian eruption
— a huge, explosive event that produces an enormous column of volcanic rock fragments and gas that reaches into the stratosphere
. The eruption produced a column that reached at least 18 kilometers into the air and deposited ash and rock fragments over 500 square kilometers. In later stages of the eruption, pyroclastic flows (pinkish rocks) and lahars (mudflows, grayish rocks) from El Azufre Volcano paved the plain to the north all the way to the Gulf of California.
s, hardened mounds of slow-moving, sticky lava. The topography in the southern part of the caldera is more rugged and irregular. The rocks are a combination of pyroclastic deposits and a slightly more fluid lava than what erupted near the coast.
satellite on October 5, 2000. The landscape is a patchwork of lava flows and the hardened remains of pyroclastic flows — hot clouds of volcanic ash
, dust, and rock fragments that race down the slopes of a volcano like an avalanche.
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
near the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
, in the state of Baja California Sur
Baja California Sur
Baja California Sur , is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. Before becoming a state on October 8, 1974, the area was known as the South Territory of Baja California. It has an area of , or 3.57% of the land mass of Mexico and comprises...
, in Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
.
La Reforma Caldera
The large La Reforma Caldera is located on the eastern coast of the central Baja California PeninsulaBaja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
, facing the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
, near Santa Rosalia, Baja California Sur
Santa Rosalía, Baja California Sur
Santa Rosalía is a city located on the Baja California peninsula, in the northern part of the Mexican state of Baja California Sur. It was named after Saint Rosalia, although the reason for the name is not quite clear since the Misión de Santa Rosalía is not located by the town, but rather in...
. The outer rim of the caldera
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
is defined by dark-colored rocks made out of very fluid lava. A dome of rock in the center of the caldera is a resurgent dome. A resurgent dome
Resurgent dome
In geology, a resurgent dome is a dome formed by swelling or rising of a caldera floor due to movement in the magma chamber beneath it. Unlike a lava dome, a resurgent dome is not formed by the extrusion of highly viscous lava onto the surface, but rather by the uplift and deformation of the...
is formed as the floor of the caldera is heaved upward by the movement of magma below ground. The lavas surrounding the caldera date to about 1 million years ago.
Tres Virgenes
The Tres VirgenesTres Virgenes
Tres Virgenes is a complex of volcanoes located Mulegé Municipality in the state of Baja California Sur, on the Baja California Peninsula in northwestern Mexico...
, a line of three connected volcanoes, collectively known by that name, are west of La Reforma Caldera. La Vírgen, in the southwest, El Azufre in the center, and El Viejo in the northeast. The volcanoes get larger and younger from northeast to southwest. As recently as 6,500 years ago, La Vírgen experienced a Plinian eruption
Plinian eruption
Plinian eruptions, also known as 'Vesuvian eruptions', are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in AD 79 ....
— a huge, explosive event that produces an enormous column of volcanic rock fragments and gas that reaches into the stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
. The eruption produced a column that reached at least 18 kilometers into the air and deposited ash and rock fragments over 500 square kilometers. In later stages of the eruption, pyroclastic flows (pinkish rocks) and lahars (mudflows, grayish rocks) from El Azufre Volcano paved the plain to the north all the way to the Gulf of California.
El Aguajito Caldera
El Aguajito Caldera is north-northeast of Las Tres Vírgenes, where pyroclastic rocks and lava date to between 500,000-800,000 years old. The rim of the caldera is not continuously exposed at the surface, but the rocks have a subtle circular arrangement. Like La Reforma, the northern rim of El Aguajito follows the coastline. The flat-looking rock formations, carved by arroyos, are lava domeLava dome
|250px|thumb|right|Image of the [[rhyolitic]] lava dome of [[Chaitén Volcano]] during its 2008–2009 eruption.In volcanology, a lava dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano...
s, hardened mounds of slow-moving, sticky lava. The topography in the southern part of the caldera is more rugged and irregular. The rocks are a combination of pyroclastic deposits and a slightly more fluid lava than what erupted near the coast.
Geography
The arid climate of Baja California limits the amount of vegetation covering the ground and allows the dramatic volcanic features of the landscape to stand out in this natural-color image from the Landsat 7Landsat 7
Landsat 7, launched on April 15, 1999, is the latest satellite of the Landsat program. Landsat 7's primary goal is to refresh the global archive of satellite photos, providing up-to-date and cloud-free images. The Landsat Program is managed and operated by the USGS, and data from Landsat 7 is...
satellite on October 5, 2000. The landscape is a patchwork of lava flows and the hardened remains of pyroclastic flows — hot clouds of volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
, dust, and rock fragments that race down the slopes of a volcano like an avalanche.
See also
- Trans-Mexican Volcanic BeltTrans-Mexican volcanic beltThe Trans-Mexican Volcanic Belt also known as the Transvolcanic Belt and locally as the Sierra Nevada , is a volcanic belt that extends 900 km from west to east across central-southern Mexico...
- List of volcanoes in Mexico
- Category: Natural history of Baja California Sur
- Category: Lava domes