Tag Archives: Geology

Catalina Schist – Rockin’ Out!

Time to turn back the clocks…to 100 million years ago! Catalina Island was formed from geological events back in the Mesozoic era when dinosaurs still roamed the Earth. The beautiful flora and fauna of Catalina Island sit on two main types of rock: igneous and metamorphic. Igneous rock is the younger of the two because it is produced from direct volcanic activity. Metamorphic rock is formed from different rocks that are subjected to various amounts of heat and pressure in the Earth’s crust. Catalina’s metamorphic rock, Catalina Schist, is found nowhere else in the world and is observed on the west end of the island.


Geological map of Catalina Island Green and yellow = metamorphic rock; Blue and pink = igneous rock

Photo credit: Catalina Island Conservancy

Catalina Schist took approximately 80 million years to form underneath the ocean’s surface as a part of violent tectonic plate activity. Three plates in the crust—North American, Farallon, and Pacific—were responsible for many of the geological features in the Channel Islands and United States west coast. As the Pacific Plate began to migrate eastward, it crushed the Farallon Plate against the North American Plate. Because the Farallon Plate was a heavy oceanic plate it sank underneath the lighter continental North American Plate, creating a subduction zone.

Heat and pressure resulted from the two plates grinding against each other for millions of years and subsequently created different kinds of metamorphic rocks. Some of these rocks formed the Rocky Mountains and Sierra Nevadas, and some bundled together to form a mélange of rocks that became the Channel Islands. The Farallon Plate eventually broke apart under the movement of the massive Pacific Plate and is now part of the Earth’s crust near Kansas! Geologic activity that produces mountainous regions is called regional metamorphism, and the Channel Islands are an excellent showcase of this process.

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Formation of Catalina Island caused by colliding crust and subduction zones

Photo credit: Wikipedia (Franciscan Assemblage)

Catalina Schist was formed about 15-30 km deep in the Earth’s crust under a medium pressure and medium temperature. There are three subtypes of Catalina Schist: garnet amphibolite, greenschist, and blueschist. Geologists determine a rock’s history and origin by looking at its crystals; how the crystal is aligned, its age, and shape will reveal the temperature, location, and conditions under which the rock was formed. During the Farallon subduction, some parts of the crust experienced more heat than others, resulting in different kinds of schist. Schist can be differentiated from other types of metamorphic rocks using the following factors:

  • Schistosity: the degree of folding and crystal alignment in a rock
  • Hardness: how much force a rock can undergo before its structure is compromised
  • Melting point: at which temperature the rock begins to disintegrate
  • Crystal structure and orientation
  • Grain coarseness: whether rocks appear grainy or solid

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Blueschist and other metamorphic rock found near Echo Lake on Catalina Island

Photo credit: Alyssa Bjorkquist

Catalina Schist is unique is found in an inverted temperature gradient, meaning that the rocks formed under hotter temperatures are found closer to the surface and cooler rocks are found deeper. Garnet amphibolite is the youngest of the Catalina schists. It is usually coarse and grainy, has bright chunks of garnet embedded in the rock, and has little to no schistosity (folding and flakiness). It is formed when exposed to an average temperature of 620ºC and was the first of the Catalina Schist to rise out of the water. Greenschist is formed around 400ºC, exhibits a high degree of schistosity (high degree of folding and flaking), and has an abundance of serpentine in the rock, giving rise to its green color.

Blueschist is one of the rarer types of rock in the world due to its unique conditions during formation. Below the Earth’s crust at 15-30 km, the temperatures are normally a sweltering 500-750ºC. However, when rocks sink rapidly below a neighboring tectonic plate in a subduction zone the temperatures can change dramatically. Blueschist forms when metamorphic rock is quickly shoved underneath a tectonic plate, heated up to 200-400 ºC (the temperature of your average cooking toaster), then brought up to the top of the crust before the entire rock has time to cool completely. This high-pressure/low-temperature situation in combination with rocks subducting and rising creates a special formation called a Franciscan series, a collection of accretionary wedges like Catalina Island that exemplify West Coast geology.


Three types of Catalina Schist, found with an inverted temperature gradient and increasing schistosity.

Left to right: garnet amphibolite, green schist, blue schist

Photo credit: Alyssa Bjorkquist

To learn more about Catalina’s geology and the types of rocks found here, explore the Catalina Island Conservancy website: https://www.catalinaconservancy.org/index.php?s=news&p=article_322

To learn more about schist, shale, and metamorphic rocks, click here: http://geology.com/rocks/schist.shtml

To learn more about blueschist and hear interesting podcasts on work being done by the U.S. Geological Survey (USGS), follow this link: https://walrus.wr.usgs.gov/infobank/programs/html/school/moviepage/17.01.28.html

Written By: Alyssa Bjorkquist


  • Allan A. Schoenherr, C. Robert Feldmuth, and Michael J. Emerson. 1999. “Natural History of the Islands of California”. University of California Press, Berkeley and Los Angeles, CA.
  • Chris Pellant. 2002. “Smithsonian Handbooks: Rocks and Minerals”. Dorling Kindersley Limited, London, United Kingdom.


Diatomaceous Earth

All of you know what earth is. Many of you know what phytoplankton are. Some of you know what a diatom is. But what in the world is diatomaceous earth?! First, let’s define what the “diatom” in diatomaceous earth means: diatoms are microscopic phytoplankton, which are incredibly common in all bodies of water. This plankton has been an important part of the food chain and the earth for millions of years! When prehistoric diatoms would die, they would fall to the bottom of their habitats, be it rivers, lakes, oceans, or ponds. Diatom cell walls are made up of silica, and after millions of years of these little guys stacking up on each other, they formed white, chalky, silica deposits that we call diatomaceous earth.

Diatomaceous Earth

On Catalina Island, we have these silica deposits located in some of our trails! In fact, if you have ever hiked our shrine loop, you can see some right from the trail. To look for diatomaceous earth, just look for white rock that is chalky and crumbly. This means that the land that you are hiking on was once underwater and surrounded by tiny phytoplankton! Whoa!

Now that we know what diatomaceous earth looks like, let’s learn about some of its uses. Scientifically speaking, it is amazing evidence that many islands came from the ocean and is a great indicator of how productive and nutrient-rich the oceans were at the time that these islands were formed. Today, humans have found a multitude of uses for this algae-turned-stone. One popular use is as an alternative to pesticides to kill insect pests. Diatomaceous earth can be easily ground into a powder and used to dehydrate insects as it can soak up moisture and oils from the insects’ exoskeletons. Furthermore, we use it many beauty products such as face washes and toothpaste as it is abrasive and can gently scrape off dead skin and plaque. Amazingly, this ancient algae chalk is edible! Farmers feed food-quality diatomaceous earth to their cows and other animals to combat parasites. We can eat this stuff as well. In fact many bakers put it in their bread, as it helps to preserve the grain. Many believe that this stuff makes you live a longer life by cleansing your colon and ridding you of parasites too!

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All in all, diatomaceous earth is quite an incredible mineral. Millions of years ago this earthen material used to be alive and well, floating and producing oxygen in all the earth’s waters. Then when they died, they stacked up on each other and were transformed into an edible, bug killing, life lengthening rock that we can see on Catalina Island… how cool?!

For more:


Mine, All Mine! – The Mining Boom on Catalina Island


Catalina Island has a very long and unique history, from the Native American peoples who lived on the island for thousands of years, to the European settlers of the 16th and 17th centuries, and even the movie stars of the mid 1900s. One brief part of Catalina’s history that is often overlooked is the mining boom of the late 1800s and early 1900s.

Mining 1

Catalina had a brief mining rush that actually predates the California Gold rush. In the 1830s, a sea otter hunter and fur trapper named George C. Yount claimed to have discovered gold-bearing quartz in the hills of the Cherry Valley cove. Most people at the time didn’t take the discovery as lightly as Mr. Yount: he only returned to Catalina three times in search of gold, but news of his discovery eventually led to a mining boom on the island.

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George C. Yount, or should we say… “The Goldfather?”

Many prospectors flocked to Catalina in search of riches, and found it quite easy to stake a claim and squat on the mostly-uninhabited island. The chances of striking a motherlode on Catalina seemed high, with many prospectors finding traces of silver and hoping it would lead them to a vein. Unfortunately for most miners, there weren’t any veins of pure silver ore, but instead major deposits of galena, which is a combination of Lead, Zinc, and Silver.

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A combination of galena (silver) and quartz (white), a likely find in a mine like Black Jack (MineralsBulgaria.com)

Galena itself did have some value, but not to the average prospector — and the mining boom on Catalina faded fairly quickly. Some mines on Catalina continued to operate throughout the years, mining for galena at places such as Black Jack Mountain and Silver Peak, the second and third highest points on the island.

The name Black Jack itself comes from another mineral that is usually found in association with galena, sphalerite. The nickname “black jack” comes from the dark appearance of this “junk” mineral that was often found attached to more valuable lead ores.

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Galena with sphalerite (zinc sulfide or “black jack”), quartz, and pyrite (Minfind.com)

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When the stock market crashed in the 1920s and the Great Depression hit the United States, the last of the mining operations ceased and mining on the island disappeared, leaving nothing except for a few holes in the ground as evidence of the Catalina boom.

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Was Catalina Island formed by a volcano?

True or False?
Catalina Island was formed long ago by an ancient volcano.

Volcanoes form some islands, however Catalina Island was formed by geologic activity that pushed the Earth’s mantle to the surface forming the island. Once that super heated rock was pushed up, it was cooled by the ocean water, which formed Catalina Island as well as the other Channel Islands. This type of geologic movement is called subduction, specifically between two of the Earth’s tectonic plates. About 200,000 million years ago, the Farallon plate, sitting under the Oceanic Plate, began to subduct, or go under the North American Plate. This movement scraped up rock and sediment from the bottom of the ocean bringing it to the surface, forming what we know today as The Channel Island chain. This type of plate subduction took about 100 million years to break the surface, and to become the islands that we walk and roam present day.

Because of this type of subduction formation, Catalina Island is made up of three different types of rock; Igneous, Metamorphic, and Sedimentary which require heat, pressure, and sediment in order to form. The most primary rock composition of the island is made up of a type of metamorphic rock called blue and green schist, located mainly on the western and central parts of the island. Catalina is also made up of quartz, located on the east end of the island and in the middle canyon.

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All of this rock talk can be lumped into a big category known as geology, or the study of rocks and how they change over time. I know, sounds kind of boring, but geology actually allows us to look into the past and understand our timeline as well as Earth’s history and place within the cosmos as we know it. Think of geology as Earth’s well-kept diary, shedding light on the secrets of land and ocean formation on our big blue planet.

Ocean Sea Floor Spreading

When you think about oceanography, what do you imagine? You probably think about whales, fish, dolphins, sharks, coral reefs, hurricanes, or even typhoons, perhaps. However, there is much more to the ocean than that. It is so vast! There are four aspects of the ocean to consider: Biological, Chemical, Physical, and Geological, and each field is interconnected. Sea floor spreading falls under geological. This encompasses the history and the structure of the ocean floor, which involves coastal areas, sediment, and the chemical processes that create the sea floor.

Earth is made-up of twelve predominant plates and there are two types. They are the continental and oceanic plates. The video above demonstrates how when two oceanic plates diverge (a divergent boundary), they create new sediment. As the two plates part, the hot liquid magma from the Earths mantle seeps to the surface cooling and solidifying this organic material as it comes into contact with cold water. The smoke is due to the reaction that occurs during the cooling. This process is called lithification. The temperature around this volcanic activity can reach up to 300 degrees Celsius. Believe it or not, but life exists under these conditions. How cool is that!

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You can find this type of boundary in the middle of the Atlantic Ocean; it is called the Mid-Atlantic Ridge. Along the ridge lie mountains beyond mountains, the majority of it unexplored. This is just one topic on oceanography out of many others! Click on the link below to learn more.

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Cite: http://oceanexplorer.noaa.gov/explorations/05galapagos/background/mid_ocean_ridge/mid_ocean_ridge.html





Geology Rocks in 15 Seconds

This Geology Rocks in 15 Seconds video demonstrates the unique geological landscape that is Cherry Cove. Once a mining community, Cherry was a large producer of Galena, a metallic mineral that is an important source of lead and, on rare occasions, silvers! Near Cherry, the rock quarry was used to harvest stones used for many things on the mainland, including Long Beach break walls.

One can find many types of stones in or near Cherry Cove; Lion’s Head, an iconic landmark of Cherry is made of blue schist, Bird Rock is made of Sedimentary Breccia, Ship Rock is composed of mostly igneous rock from volcanic activity, and one can find Diatomaceous Earth, rock made from the remains of dead plankton, within the walls of Little Fisherman’s Cove. There are many more different rock types that can be found on Catalina Island, ranging from the iridescent emerald of Green Schist to the soft textured Soapstone.


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