Geology

The Baja Peninsula separated from mainland Mexico and opened up the Sea of Cortez some 5–10 million years ago in the Cenozoic Age, as the result of a gradual shifting of land masses called plates. The process, called plate tectonics, began as far back as the Mesozoic Age (63–230 million years ago), when the North American and Pacific Plates began to collide, pushing up mountains from Alaska to the tip of Baja.

As the collision took place, the thicker North American Plate rode over the thinner Pacific Plate, forming a new landmass prone to volcanic activity along volatile faults such as the San Andreas, which runs through the middle of the Sea of Cortez. Over a period of tens of millions of years, the Pacific Plate drifted northward, tearing Baja from the mainland of Mexico. About five millions years ago, Baja pulled far enough away from the mainland to open up the Sea of Cortez.

Many of the islands we see today were formed during the last ice age, when low-lying valleys filled with water, leaving only the highest points along the coast exposed.

Baja continues to drift northward today as part of the Pacific Plate, and geologists predict it will eventually become an island, proving the early Spanish explorers right.

Geography

The lower California peninsula stretches 1,300 kilometers (806 mi) from top to bottom. It begins at Tijuana at the border with the United States and extends 193 kilometers (120 mi) east to Mexicali and south to the cape at San Lucas below the Tropic of Cancer. Baja lies 250 kilometers (155 mi) west of mainland Mexico at its greatest distance. In between is the Golfo de California (Gulf of California), more commonly known as the Mar de Cortés (Sea of Cortez). On the west coast of the peninsula is the Pacific Ocean. At its narrowest point, between Bahía de La Paz and the Pacific Ocean, the peninsula measures just 45 kilometers (28 mi) across.

Numerous mountain ranges (23 to be exact) run the length of the interior, from northwest to southeast, with the highest peak, Picacho del Diablo, rising more than 3,000 meters (10,000 ft.). The longest and highest ranges include the Sierra de Juárez and Sierra de San Pedro Mártir in the north, the Sierra de la Giganta in the central peninsula, and the Sierra de la Laguna in the south.

At the foot of the sierras are vast desert areas comprising about 65 percent of the peninsula. The San Felipe Desert covers much of northeastern Baja, while the Gulf Coast Desert extends from Bahía de Los Angeles to San José del Cabo in the south. The Vizcaíno Desert, in the west-central part of the peninsula, is Baja’s largest desert area and has been designated a protected Biosphere Reserve by the United Nations. South of this area, the Magdalena Plains (Llano Magdalena) border Bahía Magdalena, the largest bay on either side of the peninsula. Together, these two desert areas are often called the Desierto Central.

In addition to these extremes, the peninsula features coastal wetlands, sandy beaches, more than 100 islands (most of them located along the Gulf coast), and deep canyons filled with palms.

The Sea of Cortez

The Mar de Cortés (Sea of Cortez) was originally named for the legendary Spanish explorer, Hernán Cortés, in the 16th century, and was sometimes also called the Mar Vermejo (Vermillion Sea) on early maps—a name that referred to the massive schools of pelagic red crabs that float on the water’s surface in the spring. The Mexican government changed the official name to the Golfo de California (Gulf of California) in the early 20th century. Both names are used on maps today.

The sea is 669 miles long, extending from the mouth of the Colorado River to the cape at San Lucas. The northern section of the sea is shallow, the result of silt deposits from the river. Tidal fluctuations are extreme, as much as six meters near San Felipe.

Around the Midriff Islands near Bahía de los Angeles, the sea gets deeper and colder, and strong currents bring more nutrients, which sustain a phenomenal diversity of life—more than 900 species of marine vertebrates and more than 2,000 invertebrates. It’s an environment that Jacques Cousteau once called the aquarium of the world.

South of La Paz, the gulf becomes more like an ocean, with deep trenches, submarine canyons, and towering seamounts.

The Sea of Cortez meets the Pacific Ocean below the tip of the Baja Peninsula, offshore from the rocky point known as Finisterra (Land’s End).

Environmental Issues

Many books, articles, and websites are now dedicated to the communication of Baja’s environmental challenges. Travelers should understand that the rapid growth of tourism and real estate development, especially in the Los Cabos area, has strained fragile ecosystems up and down the peninsula.

Coastal development threatens the mangrove habitat on the Mogote Peninsula near La Paz and the Estero San José. The delicate coral reef offshore from Cabo Pulmo could deteriorate rapidly if the water gets polluted from ongoing beachfront development. Even the pristine islands offshore from La Paz are showing signs of stress from the increase in camping and organized trips.

On both sides of the peninsula, endangered sea turtles face poaching and loss of habitat for laying eggs. Commercial fishing has taken a toll on other species as well, with prized billfish reportedly now much smaller in size than in the early years of Baja’s fishing camps. Desperate to make ends meet, poachers take illegal reef fish, flying mobula rays, lobster, and desert pronghorn.

At the same time, aggressive international corporations negotiate with the Mexican government for licenses to use harmful longline fishing techniques in the Sea of Cortez, which destroy all manner of marine life. Conservationists are routinely called to help rescue whales, whale sharks, and dolphins from these nets.

In the long term, the scarcity of freshwater and ability of municipalities to keep up with water and sewage treatment needs pose another concern. Communities from Los Cabos to La Paz have banded together to fight the potential of open-pit gold-mining in the Sierra de la Laguna, which could contaminate drinking water with arsenic.

On the bright side, gray whales have made a remarkable comeback, and reefs are showing signs of recovery as local groups team up with the government to provide education and training so that fishermen can earn a living as ecotour guides instead of poaching.

Residents and visitors, both Mexican and foreign, are getting involved to help conserve the environment for years to come. For example, Grupo Tortuguero (www.grupotortuguero.org) runs a turtle conservation program in Baja, and Pro Peninsula (www.propeninsula.org) publishes an informative website and quarterly newsletter about Baja’s environmental concerns.

Comunidad y Biodiversidad A.C. (COBI, www.cobi.org.mx) is a Mexican non-governmental organization (NGO) that promotes marine conservation throughout Baja California Sur. Another NGO, Rare Conservation (www.rareconservation.org), uses grassroots methods to promote sustainable fishing within marine parks in the Gulf of California.

Climate

The most important feature of Baja’s climate for most travelers is its abundance of warm, sunny, dry days. In fact, your chances of enjoying a winter beach vacation without rain are higher here than in Hawaii or Florida. (Wind is another matter, however.) Across the entire peninsula, the climate ranges from Mediterranean to desert to tropical.

In general, the mountains are cooler than the coast, the Pacific coast is cooler than the Gulf coast in summer (but can be warmer than the Gulf coast in winter), and the northern part of the peninsula is cooler than the southern part. But within these guidelines are numerous microclimates, caused by the interplay of mountains, bays, currents, fog, and winds.

In summer and fall, tropical storms called chubascos can bring rain and high winds for a few hours to a few days at a time. Hurricanes are less common, but they do occur every few years. The most recent one to strike Baja was Hurricane John in 2006, which made landfall at Cabo Pulmo, bringing heavy rains and 150-mph winds all the way to Mulegé and Santa Rosalía.