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San Diego Phenomena

Phenomena in Science Education

Phenomena are the natural and man-made observable events that provide context for the work of scientists and engineers. Recent science standards changed the focus from learning about science to figuring out science. Phenomena are a powerful way to engage students and empower them to wonder and investigate.

Sometimes, we look too hard for the phenomenal events and miss the every-day occurrences that are just as intriguing. The list below is a constant work in progress and will be updated as new submissions are received and new occurrences are observed in and around San Diego County.

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Trees Get Most of Their Mass from the Air

Image: Fleet Science Center

The Moreton Bay Fig Tree, located behind the San Diego Natural History Museum in Balboa Park, is one of the largest fig trees in North America. When the tree was last measured in 1996, its crown was 123 feet (37 meters) wide. For comparison, nearly three yellow school buses measuring 45 feet (14 meters) long each could fit underneath end-to-end!

Balboa Park’s Moreton Bay Fig Tree started as a tiny seed more than 100 years ago. Since then, it has gained a tremendous amount of mass.

Where does most of that mass come from? Consider these three statements:

  • Trees get most of their mass from the soil.
  • Trees get most of their mass from the sun.
  • Trees get most of their mass from the air.

How can we plan an investigation to discover which statement is correct?

Many years ago, scientist Jan Baptist van Helmont experimented by watering and weighing a potted tree over time. After five years of tree growth, van Helmont discovered the potted tree weighed significantly more than when his experiment started. What does van Helmont's experiment say about the three options above?  How can additional experiments reveal more about how trees gain mass?

Note: Trees need many resources to grow, however the majority of a tree's dry mass comes from one of the sources above. Dry mass does not include water. The percentage of water in trees varies greatly and that calculation is beyond the scope of this entry.


MSU: Where Do Trees Get Their Mass From?

YouTube: Where Do Trees Get Their Mass From?

BBC: Van Helmont's experiments on plant growth

Balboa Park: Moreton Bay Fig Tree


NGSS & Grade

5-LS1, LS1.C: Organization for Matter and Energy Flow in Organisms


Pineapple Express

Image: NOAA

There are rivers in the sky called atmospheric rivers.

What causes an atmospheric river? Why is this band of moisture confined to a narrow strip, sometimes only a few hundred miles across? How does California’s topography influence an atmospheric river and contribute to rainfall and snowfall in the state?


Image: GOES-West, NASA

Look for the narrow band of clouds originating naer Hawaii (center left). Those clouds, filled with tropical moisture, travel to the coast of California as an atmospheric river. This weather phenomenon is nicknamed the Pineapple Express and is a contributor to the California water cycle. Occasionally, an atmospheric river reaches San Diego.


NOAA: What are atmospheric rivers?

NOAA: Atmospheric river portal

YouTube: GOES-West Satellite Sees Pineapple Express

NGSS & Grade

MS-ESS2, ESS2.C: The Roles of Water in Earth's Surface Processes

MS-ESS2, ESS2.D: Weather and Climate

Pumpkin Patch near Anza-Borrego

Image: ExploreCalifornia.pics

Just outside of Ocotillo Wells, near Anza-Borrego Desert State Park, sits a geologic phenomenon called the Pumpkin Patch due to the rocks’ size, shape and distribution in the field.

How did these rocks form? Why are the rocks a consistent shape and size and how do natural processes continue to expose more of these rocks over the years?

These rocks are a unique geologic feature called concretions, which form when layers of sediment build up around a nucleus like a pebble or a shell. Erosion from wind and water expose these rocks. Similarly, erosion shapes the concretions. Eventually, the same forces that expose the concretions will wear away each of these uniquely shaped rocks.


Desert USA: Concretions

Paleontological Research Institution: Concretions

The Adventure Portal: The Pumpkin Patch

NGSS & Grade:

4-ESS2-1, ESS2.A: Earth Materials and Systems


Great Whites Gather in the Pacific

Image: Tagging of Pacific Predators - TOPP

Trackers on great white sharks in the Pacific reveal that sharks gather in a remote location every year near the mid-point between San Diego and Hawaii.

For years, scientists from Stanford University’s Hopkins Marine Station and the Monterey Bay Aquarium used electronic tags to track the sharks along the California coast. Sharks would feed on seals and sea lions in the coastal waters near San Francisco.  For unknown reasons, the sharks would leave these lucrative feeding ground for a section of ocean roughly the size of Colorado. The sharks would congregate in what was thought to be a food desert. But why? What would cause a shark with a voracious appetite to travel to a random location in the middle of the Pacific dubbed the ‘White Shark Café’?

Why do people move around, and how might those needs be similar to those of the great white? Learn more about the White Shark Café using the links below.


MBARI: Researchers describe abundant marine life at the “White Shark Café”

Schmidt Ocean Institute: Voyage to the White Shark Café

NPR: Great White Sharks Have a Secret ‘Café’ and They Lead Scientists Right To It

LiveScience: Great White Sharks Gather in Droves in the Middle of Nowhere, But Why?

TOPP: Tagging of Pacific Predators 



Pacific coast is colder than Atlantic coast

Image: Google Maps

What does Earth's rotation have to do with ocean temperatures off San Diego? 

The average water temperature off Scripps Pier in September is 66 F. Follow San Diego’s line of latitude (32.7 N) over to Charleston, SC, and you will experience an average water temperature of 82 F. The sun’s rays hit both locations at the same angle, so what other factors contribute to the difference in water temperature?

The quick answer to explain the difference in coastal water temperature is to track the water’s path. Ocean water off San Diego comes from Alaska. Ocean water off Charleston comes from the Caribbean. This explanation opens new questions, like why does water move up the coast on the east but down the coast on the west?

You can explore global ocean circulation through density experiments and through the phenomenon known as the Coriolis effect:

  • Water near the polar regions increase in salinity, and in turn density, because when saltwater freezes it leaves behind salt. This causes denser salty water to sink to the bottom and new water to rush in. This helps explain the circulation in a north-south direction. But why does water travel up one side of a continent and down the other side?
  • As the Earth spins, the Coriolis effect kicks in. As Earth rotates, water at the poles rotates at a slower speed than water near the Equator. This difference in speed causes water to deflect to the right in the northern hemisphere and deflect to the left in the southern hemisphere. The animated photo above is a Coriolos fountain, a visual demonstration of this phenomenon. What direction do you think the spouts of water will go when the fountain is turned? What direction does the water actually go? Why?

Coriolis Fountain. Image: Hector Maciel, YouTube

Need additional visuals to support the Coriolis effect? Use imagery of hurricanes and typhoons in both the Northern and Southern hemispheres. What is similar? What is different? What direction do each spin?


NOAA: Average Water Temperatures, South Carolina and Georgia

NOAA: Average Water Temperatures, Southern California

NOAA: Surface Ocean Currents

NGSS & Grade:

MS-ESS2-6, ESS2.C: The Roles of Water in Earth's Surface Processes




Coyote sightings in residential neighborhoods

Image: Dustin Kircher, Nextdoor

San Diego residents reported an increase in coyote sightings in suburban neighborhoods in mid-2018. According to University of California’s Coyote Cacher database, sightings were made in City Heights and Kearny Mesa in July. Additionally, local news reports and social media platforms like Nextdoor documented sightings as far west as Clairemont.

The San Diego Humane Society, currently operating as animal control in most of San Diego County, claims the following conditions are contributing to the rise in sightings:

  • The West Fire in Alpine in July 2018 drove coyotes westward.
  • Increased heat and drought conditions in the summer of 2018 make food and water scarcer.

Where do coyotes fit in an ecosystem and what changes to the ecosystem might account for coyote movement into suburban environments?

Some claim coyote activity is not increasing but instead increased access to technology makes coyote sightings easier to report. Online databases like Coyote Cacher and social media platforms like Nextdoor allow neighbors to share sightings, creating a perception of increased coyote activity. 

For the Classroom:

Claim-Evidence-Reason - Is there an increase in coyote activity in suburban San Diego neighborhoods or has technology created a perception of increased activity? 


University of California: Pest Management

University of California: Coyote Cacher

ABC News: Coyote sightings expected to increase during heat and drought, August 2018

NPR, KPBS: Coyote sightings on the rise in San Diego, July 2018

San Diego Union-Tribune: Call of the coyote: living with the urban and suburban coyote, April 2018

NGSS & Grade:

2-LS4, LS4.D: Biodiversity and Humans

5-LS2, LS2.A: Interdependent Relationships in Ecosystems

MS-LS4, LS4.C: Adaptation


King tides: high tide and low tide vary

Image: The Marine Room

While cycling into work one day, a staff member at San Diego Coastkeepers noticed that a section of the bikeway was under water. The cyclist hadn't seen water in this spot before and wondered what the cause was. 

The flooding was the result of a king tide. King tides are the highest of high tides that are naturally-occurring and predictable. The moon's position in relation to Earth is responsible for all tides, including king tides.

Why does the height of high tide vary? What is the relationship between the Moon and Earth that causes this variance? 


San Diego Coastkeepers: The King Tides Are Coming

NOAA: What is a King Tide?

California King Tides Project: Schedule of tides

NGSS & Grade

5-ESS1-2, ESS1.B: Earth and the Solar System

MS-ESS1-1, ESS1.B: Earth and the Solar System 

Monarch Butterflies migrate great distances

Image: Paul Mirocha

Each year, thousands of Monarch Butterflies choose San Diego as their overwintering site. In August, Monarchs arrive after traveling 1500 miles or more. Monarchs are known to return to the same location--and even the same tree--year after year. What makes this migration more amazing is that no single butterfly makes it more than once. Due to the short life-cycle of the butterfly, each migration is made by Monarchs three or four generations apart. 

What causes Monarchs to migrate in the first place? How do Monarch butterflies know when to migrate and how do the butterflies know to return to the same spots? How do butterflies, weighing less than an ounce, travel dozens of miles each day? 

The Fleet Science Center's film Flight of the Butterflies explores this migration and features the scientists who work to track them. Flight of the Butterflies is one of many films available for school group visits.  


Monarch Watch: Migration and Tagging

Paul Mirocha: Where do Monarch Butterflies Go?

NGSS & Grade:

K-LS1, LS1.C: Organization for Matter and Energy Flow in Organisms

K-ESS3-1, ESS3.A: Natural Resources

Green flash appears on the horizon


In the fleeting seconds just as the sun dips below the horizon, you may catch a brief green flash. This phenomenon, visible at both sunrise and sunset, is so famous yet so elusive in San Diego. Local restaurants and breweries have even adopted the name for their businesses. Sunset Cliffs in Point Loma is a popular location for spotting the green flash, although social media posts indicate it is visible from Ocean Beach, too. 

What causes the green flash? Why is it visible sometimes but not all the time? Popular sighting locations along Point Loma are above sea level -- does that vantage point make the green flash any easier to spot?


EarthSky: How to see a green flash

LA Times: Wait for the green flash on the Sunset Cliffs in San Diego

ABC News 10: Where to see a green flash in San Diego

San Diego Reader: San Diego's Green Flash Phenomenon

Times of San Diego: Rare green flash at sunset dazzles San Diego

NGSS & Grade:

MS-PS4, PS4.B: Electromagnetic Radiation