Getting a handle on deep time

30 March 2026

Sam wrote to ask, “I wonder about the gradual understanding of ‘deep present’ and of geologic time and presence, the change in perspective of how the world feels around you as you gain more and more understanding of it. I wonder if you can recall this experience of your early education in geology or perhaps further understanding of Oakland’s particular geology, and the feelings that came along with having a grand and deep understanding of what goes on below you.” He wondered if I remembered a “click” moment.

There’s a famous moment in the history of geology from 1788, recounted by the Scottish mathematician John Playfair. He was with an outing led by the geologist James Hutton along the coast of Berwickshire. As their boat passed a place called Siccar Point Hutton spotted a key feature — a dramatic angular unconformity — in the rocks there, something he’d been seeking for years.

Hutton explained to the group what it meant. Sediment had been laid down in an ancient sea and hardened into sandstone. Then the seafloor had risen above the water, tilting the sandstone beds and exposing them to erosion. Then the land had subsided again and new layers of sediment were laid down upon the former land surface. They too gradually had hardened into sandstone. Then the seafloor rose once again and exposed the telltale contact between the two sets of rocks, tilted at two different angles, at Siccar Point.


Aerial view of Hutton’s unconformity at the coastal promontory of Siccar Point in the Scottish Borders. (Photo Source: UKRI© British Geological Survey (P1020257). From IUGS Geoheritage site.

Each one of these events must have taken an immense length of time. No doubt Hutton waved his arms, gestured with his hands, and expressed astonishment at his own insight. Playfair wrote, “The mind seemed to grow giddy by looking so far into the abyss of time; and while we listened with earnestness and admiration to the philosopher who was now unfolding to us the order and series of these wonderful events, we became sensible how much farther reason may sometimes go than imagination can venture to follow.”

Reason guided my imagination as I gained my sense of deep time, in geology school and afterward. The evidence shows that Earth operates at a slowness we can’t perceive, only infer from careful measurement. In 1788 there were clues but few measurements: ancient ruins in Italy had subsided into the sea and emerged again. Ancient harbors had filled with sediment shed from the mountains. Rocks recorded the same kinds of changes at even more remote times, and they contained fossils unlike any living creatures. Clearly the stories in the book of Genesis — the seven days of creation and the generations after Adam and Eve — weren’t meant literally. But geologists resisted thinking in millions of years until the kind of evidence Hutton had seen was repeated around the world, leaving no alternative.

For me, the landscape is what speaks its story directly.

Landslides in the hills, cracks growing along the Hayward fault, mud carried down the creeks to the Bay by floods all testify to the geological processes working on the landscape. It isn’t hard to multiply these changes a hundredfold, then a hundredfold again to begin sensing time at Earth’s inhuman scale. It’s easier for us than it was for Hutton’s generation because our measurements are better. Knowing that the Hayward fault shifts the rocks by about ten millimeters a year, and that the Oakland Hills are rising by about a millimeter a year, it’s a simple exercise to rearrange the landscape and superimpose upon it the long ice-age cycles whose pace we also understand. A million years — a thousand millennia — isn’t out of reach. The deep present is something I believe we can all learn to feel.

When it comes to deeper time, I don’t think even geologists really grasp the millions and billions of years we reliably know about in Earth’s history. They’re just numbers, abstract and schematic, but with time and effort we can become comfortable with them. Geologists have done this and gotten past Playfair’s astonishment. Reason is what allows us to imagine the deep past, but the wonder is still within reach and worth reaching for. One avenue to wonder is fossils, and Oakland has our share.

Posted in Deep Oakland | 2 Comments »

Where to visit the Hayward fault by bus

16 March 2026

In Deep Oakland I led off the book with a chapter on the Hayward fault, the prime mover that continually makes our landscape. Yes, the Hayward fault is primed to give us a major earthquake. It’s scary to think about. I said, “I know why people prefer not to think about the fault. Every time I visit it, no matter where, I push down the dread. But once I do that, there is room for wonder and interesting things to see.”


Fault creep is damaging Broadway Terrace at the south entrance to Lake Temescal Regional Park

Yes, I visit the fault and you can too. Some places it’s obscure, and others it’s as plain as can be. From Richmond to Fremont, AC Transit bus lines will take you to the fault’s whole length and safely home again. In this post I will present seven maps showing just where the fault runs within Oakland’s city boundaries and what buses will take you to or near it. The bus stops are labeled with the line that serves them — unlabeled stops are served only by school-bus routes.

Map 1 shows the Claremont Resort by the edge of Berkeley, served by the 36 and E lines. Look for curb offsets and related street repairs on Stonewall and Alvarado roads.

Map 2 shows the Montclair business district, served by the 18 line. Fault features include curb offsets and some warped buildings, and the pond in the park was dug in a natural dip in the terrain: a sag basin.

Map 3 shows the LDS temple area at the top of Lincoln Avenue, accessed by the 31 line. See a few curb offsets and surface cracks here, or venture southward for a look at the historic landslide area.

Map 4 shows how the 54 line serves the Jordan swale, a sag basin east of a shutter ridge, and Redwood Heights. The 39th Avenue crossing at the south end has a classic offset curb.

Map 5 shows the Castlemont hill and Oakland Zoo area, served at each end by the 46L line. You can also walk to the north end from stops on the 57 or 98 lines at MacArthur Boulevard and 82nd Avenue, or to the south end from stops on the 57, 90 or 98 at MacArthur and 98th Avenue. There are bent curbs, aligned landforms and the widely offset course of Arroyo Viejo in this area.

Map 6 shows the lower Chabot Park neighborhood south of the zoo, accessible from the Foothill Square bus stops. The residential area holds a clearly visible sag basin, and multiple trails visit the offset hills and stream valleys to the south.

Map 7 shows the same wildland south of Chabot Park plus Sheffield Village, reachable on the 34 and 35 lines. The spur north of Marlow Drive leads into the wilds, while Revere Avenue at the eastern edge displays street and curb cracks.

Collect them all, by bus or by bicycle or scooter. The U.S. Geological Survey has a KML file for the Hayward fault, to load into Google Earth, that made this post feasible. For the most part, the fault locations are approximate, give or take up to tens of meters.

Let’s get to know the fault while it’s still sleeping (and creeping).

Posted in Hayward fault | 3 Comments »

Ocher quarry update

2 March 2026

The former campus of Holy Names University, in the hills just above the Warren Freeway, has been for sale for a while, but no one seems to want to move an existing college or start a new one there. The owners of “The Oakland Hills Campus,” BH Properties, just filed plans to put low-density housing there and preserve a few of the old buildings. Left unsettled are the even older presences on the property: the Peraltas’ old chapel and the Ohlones’ ancient ocher quarry.

Right now the property is gated but not posted, so I went there to look at the old places. I first featured the quarry here 15 years ago, when I didn’t know much about it. That was in autumn; the photos today are in just-spring.

The quarry site is uphill 150 meters from the old chapel (more about that later), by a playground behind the former Raskob Learning Institute. I call it a “site” and not a quarry because the evidence points to the boulders being moved here when the campus was built in the 1950s. I think the original quarry site was more spread out and is now covered by buildings. Take a look at the bare terrain, as revealed in the digital elevation model.


From nationalmap.gov; illumination from northwest

Old maps show that the ravine in the middle, where a tributary of Lion Creek runs, used to dominate the scene. Today the stream is culverted and almost everything around the campus has been uprooted or buried, but in 1897, the earliest USGS topographic map shows the chapel site as a low rise above a gentle swale stretching to the southwest. The freeway excavation obscures what was originally a saddle between the headwaters of Peralta and Lion Creeks.

Local historian Dennis Evanosky says that Antonio María Peralta, the Mexican rancher who first possessed this part of Oakland, called the place “Loma Colorada,” suggesting that this “red hill” is where the Ohlones produced ocher from boulders exposed here. And the good stuff is really red.

Dennis says Peralta held on to this parcel longer than his other lands. The chapel he built here was a noted landmark, with an inspiring view. And like Indian Gulch, this place must have been unusually significant to Peralta’s unpaid Ohlone workers. They remembered the traditional uses of ocher in body paint, sunscreen, dyes, medicine and burials. This ocher patch had been their regional monopoly, supporting rich trade connections throughout the Bay area.

Some of the boulders have hollows in them where the quarriers pounded and harvested raw material.

I suspect that the boulders have been turned, though there’s no easy way to be sure. The typical mortar holes we picture, used to turn acorn into meal, needed the hardest rock, and they needed to face upward, like the example below from Berkeley’s Mortar Rock Park. Grinding soft red rock into grit to collect in baskets is a whole different operation, it seems to me, and the hollows face different directions.

The boulders aren’t consistent in their composition, nor are they consistent with the bedrock exposed just downhill. They’re spaced artfully and don’t form any sort of pattern, the way they might if they were exhumed by erosion as an ensemble. In short, I interpret the quarry site as a modern artifact.

Still, the boulders are pure and distinctive, unlike any other place in Oakland, and they’re at the far north end of the Leona volcanics that give rise to our ocher occurrences. (See my backgrounder on how ocher forms.) I surmise that the boulders emerged at this spot because the bedrock was fertile, the topography retarded erosion and the ocher evolved gently to a better state of purity, then weather out in large bodies ready to use.

The Ohlones harvested ocher here for thousands of years, a kilo at a time. Suddenly the Spanish arrived and took them all to the San Jose Mission, the king gave the Peraltas the land, and when the missions failed the surviving Natives became the Mexican ranchers’ serf class. Antonio Peralta set up a chapel here for Catholic priests, who visited regularly. Eventually the land came into American hands, and in 1908 an architect born in Ontario named George Edward McCrea (1871-1943) bought it and built a house here for his family, adding rooms over the years. A nearby plaque says the house incorporated the chapel’s foundation.

In 1943 McCrea’s surviving son Robin gave the “ancient Indian camp” to the city of Oakland for use as a park. It appears on a 1950s road map as McCrea Park, but the city did little to improve it. A few years later the College of the Holy Names sold their original location on Lake Merritt to the Kaiser conglomerate and sought this land for their next campus. The city sacrificed the park for the college, inducing Robin McCrea to deed the land to the college and substitute a parcel on Lion Creek in its place, which is today’s McCrea Park. (It’s conceivable that some red boulders were brought up from there.)

The college burgeoned and thrived (until 2023), but in all of its bulldozing and landfilling did little to preserve the historic assets. The McCrea house, once a charming farm cottage, is in poor shape today, between decrepit and tumbledown, and the Ohlones’ camp is wiped out except for the cluster of boulders. BH Properties would turn it all to an ungainly meld of public cultural center and suburban sprawl, with no room left for the aboriginals.

The tribes haven’t forgotten this place, as I learned years ago. The Ohlones were recently granted a 4-acre reserve in nearby Joaquin Miller Park. They gave it a name in the local Chochenyo language, Rinihmu Pulte’irekne, “Above the Red Ocher.”

Posted in Geoheritage, Quarries and mines | 2 Comments »

Charles Burckhalter, Oakland science hero

16 February 2026

The name of Charles Burckhalter might ring a bell for Oaklanders: Burckhalter Elementary School, in East Oakland on Burckhalter Avenue, is named for him. I visit nearby Burckhalter Park, whenever I’m walking in the area, for its water fountain and its view of the former Leona Quarry.


Burckhalter Park, 2018

Astronomers remember him, and asteroid 3447 Burckhalter is named for him. He’s an important figure in our city’s history who has a little-noted geological connection.

Charles L. Burckhalter (1849-1923) was a farm kid from Ohio who came to work at his brother’s general store in Truckee in the late 1860s. There he spent evenings with a local attorney who stargazed with a five-inch* telescope — imagine how the night skies looked up there back then — and found a passion for astronomy.

After his marriage to Mary Catherine Nash in 1878, he moved to Oakland and took a job at a San Francisco insurance company. He built a 4½-inch telescope, mounted it in his Chester Street back yard on a stout brick foundation under a steerable canvas dome, and had himself a genuine observatory. By 1883 he’d upgraded to a 10½-incher, a very large instrument for an amateur, and made observations worthy of publication in the scientific journals.

At this point the city hired Burckhalter to teach geography and astronomy at the high school, at 12th and Market Streets, and help out at the new public observatory that Anthony Chabot had built in Lafayette Square for the citizens of Oakland in 1883. His star had really begun to rise.


Plaque at Lafayette Square on 11th Street

He was named Director of the Chabot Observatory in 1887 and served for thirty-five years, the rest of his life. He started the tradition of giving lectures on cloudy nights, using lantern slides to show audiences the wonders of the sky. He never got a college degree, but the papers often called the beloved teacher “Professor Burckhalter.”

Burckhalter’s interests went beyond the sky to the air and the Earth. His weather observations were a monthly feature in the newspapers, and he took note of earthquakes too (see an example from 4 January 1906). He installed a seismograph at Chabot Observatory in the 1880s, at the time a newfangled contraption. Astronomers were some of the earliest users of seismographs because large telescopes are precision instruments that notice even tiny disturbances. Lick Observatory, newly built in the mountains east of San Jose, had one too. Later that year, in the wake of the San Francisco earthquake, he took part in forming the Seismological Society of America and served on its founding board of directors.

1906 was a special year for Burkhalter that began routinely. He announced a lunar eclipse for the night of February 8-9. That night, the Tribune reported, he turned off the doorbell and “trained his telescope on the surface of the diminishing disk to discover, if possible, [whether] frost forms around the lunar volcano Linne.” On the last night of March he was in Berkeley at the annual meeting of the Astronomical Society of the Pacific, an organization formed by his enthusiastic inspiration.

Eighteen days later, the San Francisco earthquake came as dawn began. Burckhalter counted 19 aftershocks over the next 13 hours. Over the next few days, the papers reported him assuring the public that there would be no “tidal wave” coming and that because earthquakes cannot be predicted (still true today), “the rumors that several more are en route should not be accepted.” Within the week, he was enlisted in the California Earthquake Investigation Commission, headed by UC Berkeley professor Andrew Lawson, along with several other prominent astronomers.

Astronomers were key people for two reasons. Their seismographs were one, but the other was that they were habitual, precise observers of time who were always awake at night and had clocks that were accurate to the second. Burckhalter and Armin Leuschner were assigned to collect as many reports as they could of the time the earthquake started, whether it was human observations or stopped clocks. When commission member Harry Reid set out to use these arrival times to determine the epicenter, only a handful of observations passed muster, but they yielded an epicenter at Olema in Marin County. It was good work considering the crude data. Today we put the epicenter a couple miles off Ocean Beach, about 30 kilometers south.

Unfortunately, Chabot Observatory didn’t yield suitable data. Its two clocks stopped at different times, and its seismograph recorded a useless scribble — but so did everyone else’s. Its instrument was a Ewing duplex pendulum seismograph that suspended a stylus over a disk of smoked glass, useful for small, simple events but overwhelmed by the 1906 quake, which shook strongly for about a full minute.


From the Lawson report, volume 3 atlas, Rumsey collection

The earthquake closed the Chabot Observatory for four months, but there was little damage and the telescopes were unharmed. Burckhalter resumed his weather reports, after skipping April, and went on in his distinguished career. As light pollution increased in downtown Oakland, he raised the money and political support to move the observatory to Leona Heights in 1915, where it remained for the next eighty-plus years. The observatory’s mission has followed Burckhalter’s educational program faithfully through directors like the memorable Kingsley Wightman and today’s leaders at the Chabot Space & Science Center.

More reading

OakWiki entry

A 1961 Tribune biography

Obituary by the Astronomical Society of the Pacific

* The inch size of a telescope refers to the diameter of its light-gathering mirror or lens.

Posted in Earthquakes | 1 Comment »

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