The Mission Trails Regional Park (MTRP) Foundation is pleased to continue its OnTopic online lecture series. These programs impart knowledge that we can use as we explore the park and other natural areas. The OnTopic lectures are free, but registration is required. Many thanks to SDG&E and donors to the Mission Trails Regional Park Foundation for making these programs possible. For information about sponsorship opportunities, email email@example.com.
Geology of Mission Trails Lecture Series with Dr. Pat Abbott
How was Mission Trails Regional Park built? The science of geology can explain it. Take some basic building blocks of elements and minerals, and then use them to build rocks. These rocks are subjected to Earth’s active processes; some build new rocks, some transform existing rocks, and some destroy rocks. The rocks of Mission Trails Regional Park record the history of this area during the past 126 million years. We will ‘build’ the modern park in these three presentations.
Rocks: The Building Blocks of the Park
Thursday, February 18 at 6 p.m.
Take eight common elements. Arrange them into different structures thus making eight common minerals. Subject these minerals to different temperatures and pressures, and form three major groups of rocks: Igneous, Sedimentary, and Metamorphic. Igneous rocks form when magma cools at the surface as volcanic rocks or below ground as plutonic rocks. Weathering decomposes and disintegrates surface rocks, then the resulting debris is moved and deposited to form sedimentary rocks. Bury rocks deeply and the elevated temperatures and pressures cause transformation into metamorphic rocks.
Earth Processes: Past and Present
Thursday, March 4 at 6 p.m.
The Earth is 4.57 billion years old. The same cycles have operated for billions of years. In the tectonic cycle, the outer shell of the Earth consists of pieces or plates which are formed and destroyed. In the hydrologic cycle, solar energy elevates water into the atmosphere; it falls as rain or snow, then flows back to the ocean under the pull of gravity. In the rock cycle, igneous, sedimentary, and metamorphic rocks transform into and from one another.
Photo: David Cooksy
Mission Trails Regional Park Forms in Four Phases
Thursday, March 18 at 6 p.m.
The site stays the same, but the rocks and processes change during the past 126 million years. In phase 1 (126 to ~90 million years ago), volcanism and plutonism build mountains. In phase 2 (~90 to 56 mya), the pull of gravity and erosion by running water reduce the mountains to hills. In phase 3 (56 to ~34 mya), the region was buried beneath a huge alluvial fan built of gravels and sands brought by a river from modern-day Sonora, Mexico. In phase 4 (~34 mya and ongoing), erosion again dominates and carves out Cowles and Fortuna Mountains, Mission Gorge, and the modern topography of Mission Trails Regional Park.
For more information about the geology of Mission Trails, you may purchase a copy of Pat Abbott’s book, Geology: Mission Trails Park at www.mtrpstore.org. You may also watch Rise and Fall of the Mountains at Mission Trails Regional Park on our YouTube channel.