Archives by date

You are browsing the site archives by date.

Geology (cont. 12)

History Geology Plants Fish Birds Restoration Project Factsheets Geology The rest of the story is in the present. Batiquitos Lagoon exists today because the ice sheets of the last ice age melted 11,000 years ago and sea level rose, flooding the deep stream valley. (This makes our “lagoon” technically an estuary rather than a lagoon, […]

Geology (cont. 11)

History Geology Plants Fish Birds Restoration Project Factsheets Geology Whenever land rises, the streams flowing across the plain cut down and make deep, large valleys. This happened along the San Diego County coastline. Then, as climate warmed, ice sheets melted and sea level rose, flooding the valley into an estuary, and causing the deposition of […]

Geology (cont. 10)

History Geology Plants Fish Birds Restoration Project Factsheets Geology The land bounced upwards frequently because of movement along the San Andreas, Rose Canyon, and other faults, raising old beaches high above sea level. Today, the old beaches lie elevated above the present beach. We can see them from the trail along the lagoon. They are […]

Geology (cont. 9)

History Geology Plants Fish Birds Restoration Project Factsheets Geology Jumping forward almost to the present, let’s look at the Batiquitos area one million years ago. This was the Pleistocene Epoch of the Cenozoic Era, and there were major climate changes. North America was in the grip of the Ice Ages. Ice sheets were sculpting the […]

Geology (cont. 8)

History Geology Plants Fish Birds Restoration Project Factsheets Geology About 20 million years ago, the Farallon Plate disappeared completely, and a large fracture zone, known today as the San Andreas Fault Zone, appeared in the Pacific floor, and cut through part of the North American continent. A slice of land began to move to the […]

Geology (cont. 7)

History Geology Plants Fish Birds Restoration Project Factsheets Geology Sea level rose and fell often during this period in geologic history, and more mud was deposited again, similar to but younger than the Del Mar Formation. Known as the Ardath Formation, it can be seen south and north of Beacon’s Beach in Leucadia. About 42 […]

Geology (cont. 6)

History Geology Plants Fish Birds Restoration Project Factsheets Geology About 45 million years ago sea level rose, and the shoreline therefore moved inland, closer to the eroding mountains. Being the “dumping ground” for somewhat faster moving water (flowing down steeper hills makes water velocity increase) meant that the sediment being deposited was coarser than mud […]

Geology (cont. 4)

History Geology Plants Fish Birds Restoration Project Factsheets Geology During the Cretaceous Period, about 100 million years ago, the continuing plate collision pushed the granitic and metamorphosed sedimentary rocks (changed by the heat and pressure of burial and squeezing) up into huge mountains, which may have been as high as the Andes of western South […]

Geology (cont. 5)

History Geology Plants Fish Birds Restoration Project Factsheets Geology About 50 million years ago, at the start of the Eocene Epoch of the Cenozoic Era of Earth’s history, western San Diego County was still attached to coastal Mexico, and was partly inundated by the ocean. (Dinosaurs had become extinct about 65 million years ago, probably […]

Geology (cont. 3)

History Geology Plants Fish Birds Restoration Project Factsheets Geology From other locations, more lava erupted and cooled into greenish-gray andesite, which got its name from similar rock found in the Andes Mountains. Not all of the melted rock came out onto the surface as lava flows. Some was trapped and cooled under miles of rock […]