Earth Observatory HomeNASAEarth Observatory HomeData and ImagesFeaturesNewsReferenceMissionsExperimentsSearch
NASA's Earth Observatory
 Earth Observatory Navigation Bar
  New Images

Isla San Lorenzo and Isla Las Animas, Gulf of California
Isla San Lorenzo and Isla Las Animas, Gulf of California Click here to view full image (179 kb)

Located in the northern Gulf of California, Isla (island) San Lorenzo and Isla Las Animas—part of the Midriff Islands—record geologic processes involved in the creation of the Baja California peninsula over several hundred million years. If you were hiking southeast to northwest along the 17-kilometer-long (10.6-mile) central ridge of Isla San Lorenzo, you would first encounter granite rocks from the Cretaceous Period (146 to 65 million years ago); this light tan rock occupies the southeastern third of the island (image center left). In the central third of the island, you would see mainly older metamorphic rocks from the Paleozoic Era (543 to 248 million years ago); these rocks are brown (image center). At the end of the hike, at the northwestern third of Isla San Lorenzo (and much of adjacent Isla Las Animas), you would find much younger volcanic and marine sedimentary rocks (yellow-brown to light brown, image center right). These rocks were formed by volcanoes and fissure eruptions in and around basins in the growing Gulf of California between 5–8 million years ago. The islands themselves were formed as a result of uplift of crustal blocks along the southeastward-trending San Andreas Fault.

This astronaut photograph illustrates the largely pristine nature of these islands. The islands are located in the rain shadow of mountains on the Baja Peninsula to the west, and arid conditions prevail through much of the year. The scarcity of water has limited human presence on the islands, and allowed flora and fauna unique to each island to flourish, particularly reptiles. The islands are also home to colonies of seabirds and seals, both of which take advantage of deep, productive waters adjacent to the eastern Baja coast. Shallow waters and high levels of nutrients can also lead to blooms of green phytoplankton; two such blooms can be seen along the coastline of Isla Las Animas (image center right, in north- and west-facing bays). Winds and currents roughen the surface waters around the islands, and sunlight reflecting off the water makes the patterns visible (silver-gray regions). Regions of dark blue water indicate calm surface conditions, or the presence of oils and surfactants that decrease surface tension.

Featured astronaut photograph ISS015-E-7928 was acquired May 13, 2007, by the Expedition 15 crew with a Kodak 760C digital camera using a 400 mm lens. The image is provided by the ISS Crew Earth Observations experiment and the Image Science & Analysis Laboratory, Johnson Space Center. The image in this article has been cropped and enhanced to improve contrast. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth.

Recommend this Image to a Friend

Back to: Newsroom

Also see
Visible Earth

Latest Images
View Images Index

Isla Blanquilla, Venezuela
  Isla Blanquilla, Venezuela

Sacramento-San Joaquin River Delta
  Sacramento-San Joaquin River Delta

2007 Rainfall Patterns in United States
  2007 Rainfall Patterns in United States

Subscribe to the Earth Observatory
About the Earth Observatory
Contact Us
Program Manager: David Herring
Responsible NASA official: Dr. Michael D. King
We're a part of the Science Mission Directorate
Privacy Policy and Important Notices

The above content is a copy of the original posting of this article as it appeared on
Contact information regarding its posting in this archive is below:
Send questions or comments about this web page to the NASA Responsible Official at
Curator: Earth Sciences Web Team
Notices: Web Accessibility and Policy Notices, NASA Web Privacy Policy