Field Trip: Geology of the Rocky Shore, Bean Hollow State Beach

When: Year round, depending on docent availability
Where: Pebble Beach lot, Bean Hollow State Beach (11000 Cabrillo Hwy, Pescadero, CA 94060)
Who: K-12. Younger children may accompany, but should stay besides their parents.
Cost: Free, but suggested donation of $1/person

"Geology of the Rocky Shore" is one of many excellent educational tours run by the Half Moon Bay State Beach staff. Its goals include identifying key geologic features, learning characteristics of igneous, metamorphic, and sedimentary rocks, and doing hands-on activities similar to geologists' work on the field.

Because this tour is south of Half Moon Bay, it isn't as frequently booked but it is well worth the extra drive! Before starting however, please note that it meets at the Pebble Beach parking lot, which is the NORTH entrance to the beach, close to the town of Pescadero. Otherwise, it's a 20 minute walk from the south end - beautiful, but nerve-wracking if you don't want to show up late, since you are the trip organizer (ahem).

As a starter, we did a pebble relay - two teams took turns passing a cupful of pebbles, but without speaking. Fun, but I could see how it led in to the next section where we talked about erosion and how it moves rocks from one place to another.

The staff then distributed "geologic necklaces" - picture cards of different geologic features in the area which we could wear around our necks. We then flipped through booklets with photos explaining the rock cycle, types of rock, and formations that we could watch for. The explanation was a little difficult for the younger children below 3rd grade to follow so they were restless, but the adults enjoyed it (one of the perks of homeschooling - learning along with our children). We then went on a walk looking for the features matching our geologic necklace, such as:

Tafoni - sandstone with holes formed by salt spray weathering.
At Bean Hollow, the waves also deposit tiny stones in the holes, like pebble apartments. 

It's not a snake, it's bitumen..
The black curve indicates organic matter that was trapped and pressurized under the sandstone

The walk was useful in helping us visualize and remember the types of rocks - it's one thing to hear about sedimentary rock being soft, but another to touch sandstone that has been weathered into fantastic shapes, or see a line or shape and recognize the processes behind it.

We then went down a short flight of steps to the pebble section of the beach. This part is a sensory wonderland for children and even adults - we could have sat there for hours, admiring the various colors and smooth textures of the pebbles which had been ground smooth by the waves.

Bean Hollow "gems" - since this is a state beach, leave them for the next person to admire

The staff then distributed trays, sieves and cards for students to classify the stones by size (boulder, cobble, pebble, granular). Students then matched the stones they had found against a chart of common rocks, which was best done by further sorting by color.

Sorting the pebbles from the boulders. Fun fact: Geologists consider a stone a "boulder" if it is the size of a clipboard - very different from everyday parlance!

The final activity was to identify rock samples. Staff explained the difference between rocks and minerals, and introduced the tools students would use to test - Mohr's scale of hardness, a bottle of vinegar, a lens to watch for fizzling. This part was done in teams, and it was fun to watch the students debate like geologists in training - arguing if a certain rock had fizzled, or was considered a certain color.

Reaching eagerly for the tools. The samples included calcite (mineral), basalt (igenous rock), sandstone (sedimentary rock) and marble (metamorphic rock)

When we wrapped up the activity, we thanked the staff and volunteers. A staff member modestly said, "We just want the students to have good memories so they can look back when they study this in school and associate learning with fun." Mission definitely accomplished! To be able to have the amazing outdoors as our classroom, and learn the language of rocks with patient teachers who answer our questions - we are thankful for all of these.

Additional ideas #1: Bean Hollow has other activities - tidepooling, or hiking the trail connecting the north and south entrances. 

Additional ideas #2: In summer, you can pick berries nearby, visit a goat dairy or try the artichoke bread at Pescadero before heading home.