Noe Valley Voice April 2005

The Kids' Page

By Laura McCloskey

Rocks in Noe Valley Over 100 Million Years Old

How old do you think the rocks around Noe Valley are? Are they older than you or your parents? Here's a hint: The rocks around Noe Valley are older than anyone you know.

The rocks we see in Noe Valley formed millions of years ago. Some of them were part of the magma, or liquefied rock, deep below the earth's surface. The magma reaches the earth's surface by oozing through cracks in the earth's crust and hardening into igneous rocks. Igneous means made by heat.

Other rocks in Noe Valley were made from sediment. Rivers carried sand through their rushing waters and deposited those sands at the bottom of lakes and seas. As layers of sediment formed at the bottom of the lakes, the top layers pressed down on the bottom layers. The bottom layers slowly hardened into what we know as sedimentary rocks.

We can see rocks that are millions of years old in Noe Valley because of the movement of the earth's crust. The crust has been broken into pieces called tectonic plates. There are seven gigantic plates and many smaller ones covering the earth, each about 50 miles thick.

Noe Valley sits on the North American plate. Long ago, when the North American plate scraped against another huge plate, the collision lifted up the rocks that now make up the hills and ridges of Noe Valley.

Even today, the earth's crust slowly shifts. Tectonic plates continue to collide with each other, and sometimes they shake the ground, causing an earthquake.

When the plates collide, there is a possibility that more rocks will be exposed and the landscape around us will change. We may find new rocks in Noe Valley as the earth continues to move.

Be a Rock Hound

You can check out the million-year-old rocks in Noe Valley. Visit the sites below with an adult and examine the rocks. What do they look like? How do they feel? Start a rock journal and sketch the different rocks you find. You could take pictures of the rocks and label the pictures with the rock types and names. Start a rock collection and organize the rocks according to their different types.

Name: Red Chert

Type: Sedimentary rock

Properties: Red or orange in color; sharp edges

Location: East ridge of Glen Canyon Park; north peak of Twin Peaks; Corona Heights Park at Roosevelt and Museum Way (Randall Museum)

Name: Pillow Basalt or Greenstone

Type: Igneous rock

Properties: Gray; rounded edges

Location: West side of Billy Goat Hill at 30th and Castro streets; south peak of Twin Peaks

Name: Greywacke or Sandstone

Type: Sedimentary rock

Properties: Reddish-tan or dark gray; falls apart into chunks

Location: Under the apartment building on the corner of 21st and Church streets; northwest side of Billy Goat Hill at 30th and Castro streets

Name: Serpentine

Type: Metamorphic rock, also the state rock of California

Properties: Blue-green in color; slick, shiny surface

Location: The slope beneath the U.S. Mint, north of the Duboce bikeway between Church and Market streets. (Note: This rock, located behind the Mint fence, can only be seen, not touched.)

Clyde Wahrhaftig, Noe Valley Geologist

Clyde Wahrhaftig (1919-1994) was a well-known geologist who lived on Valley Street in Noe Valley. A geologist is a person who studies the history of the earth as recorded in rocks.

From 1942 to 1980, Clyde explored rocks in Alaska for the U.S. Geological Survey, a government agency that provides facts about geology. He also was a professor at the University of California at Berkeley from 1960 to 1982.

Clyde gave geological advice to the staff of the Golden Gate National Recreation Area, and was instrumental in preserving open spaces throughout San Francisco, including Billy Goat Hill in Noe Valley. He wrote many articles and several books about geology.

An early environmentalist, Clyde encouraged people to use public transportation. He thought walking or riding a bike was healthier and more earth-friendly than driving a car. He never learned to drive and instead got around on foot or by bus. Along the way, he wrote a guidebook called A Streetcar to Subduction and Other Plate Tectonic Trips by Public Transport in San Francisco. In the book, Clyde shows how to take a tour of the rocks forming the hills of San Francisco--by bus and streetcar.

A Streetcar to Subduction provided many of the geological facts for this Noe Valley Kids' Page.

Clyde loved guiding people to interesting geological sites. He led trips in California and Alaska. We hope Clyde Wahrhaftig would enjoy being a part of the first edition of the Noe Valley Voice Kids' Page.

Kid Collectors

There are many kids in Noe Valley who have rock collections. The Voice talked to a few who are students at Alvarado and Fairmount schools. Here's what they said about their rock collections.

Jack Bragagnolol, 9, organizes his rocks according to how much he likes them. "The first is the coolest, and the last is the ugliest." Jack points out that a lot of rocks in Noe Valley are red, which means there is iron in the earth.

Jorge Mora, 7, organizes his rock collection in a bag and a big box. He finds many of his rocks on the street.

Mary Louise Ferreir-Wallace, 10, organizes her rocks according to their color and shape. Mary knows the rocks in Noe Valley "come in different colors, sizes, and shapes."

Antonella Boucher, 11, organizes her rocks according to color and size. Sometimes she tries to find out if you can use rocks to draw pictures.

Morgan Dang, 9, organizes his rocks according to their size. "I place the large rocks in an enormous pot and the small ones in my chest of drawers."

Elynn Hagelshaw, 11, doesn't collect rocks, but instead collects crystals. One of the crystals she has grew inside a rock.

Ruary Girling, 6, separates his rocks by color. He collects rare rocks that he finds special. He knows that a lot of the rocks in Noe Valley are hard.

Useful Books on Geology

All of these books can be found at the public library. Books with an asterisk are written for children.

*Earthquakes by Deborah Heiligman

*The Big Rock by Bruce Hiscock

*How Mountains Are Made by Kathleen Weidner Zoehfeld

*Let's Go Rock Collecting by Roma Gans

*Planet Earth/Inside Out by Gail Gibbons

A Streetcar to Subduction by Clyde Wahrhaftig

Geologic Trips: San Francisco and the Bay Area by Ted Konigsmark

Special thanks to Anna Sojourner, an engineering geologist with Caltrans; to Richard Craib with Friends of Glen Canyon Park; to Noe Valley history buff Bill Yenne; and to Doris Sloan and Margaret Gennaro, of U.C. Berkeley, for supplying photos and information about Clyde Wahrhaftig.