On March 6, Tim Elam gave a presentation titled “Life on the Edge” at the Buena Vista Museum of Natural History. Elam calls himself a “semi-retired geologist,” and has had 28 years of experience working in the oil industry.

Elam encouraged his audience to ask questions throughout his presentation, which many viewing did. There were also a few who answered some of the questions.

Before he got into his presentation, he gave a brief summary of the science of earthquakes and tectonics in general. He told the audience, for instance, about the three main types of plate motion. In transform boundaries the adjacent plates grind past each other; in divergent boundaries the plates pull away from each other; and in convergent boundaries the plates collide, resulting in a subduction zone, where one plate is forced below the other. The San Andreas Fault is the first of the three, more specifically a “right-lateral strike-slip (or transform) fault,” according to Elam.

He also mentioned the more recent earthquakes. The earthquake in Haiti, he said, was so devastating because it was a relatively shallow earthquake, meaning it happened very close to the earth’s surface, while the Chilean earthquake was significantly less so because it was much deeper in the earth’s crust and the epicenter of the quake was not nearly so close to a highly populous area.

After that, Elam began to discuss the fault most Californians have heard of plenty of times before: the San Andreas Fault.

The fault has been active anywhere from 15 million to 20 million years, depending on which geologist you ask, and it currently results in plate movement of about 2 inches a year. That means that the North American plate, which is the plate that most of America sits on, is sliding past the Pacific plate “as quick as a fingernail grows.”

“This means, whether they like it or not, L.A. and San Francisco will be neighbors in about 10 million years,” said Elam.

The plates move because of the convection current (a cycle of heated mantle rising, then cooling, falling, heating, and then rising again) within the earth’s mantle, which is the semi-solid material between the earth’s crust and core. This “heat engine” is what drives the plates to move the way they do.

Elam showed the audience an animation depicting the long history of the fault, which has not always been (and will not always be) the physical expression of the Pacific Ocean/North American continent boundary. Over the course of 40 million years, the Pacific plate, the North American plate, and the now gone Farallon plate, converged until the Farallon plate was entirely subducted under the North American plate. What took millions of years to occur seemed a dramatically fast transformation of the west coastline.

A woman in the audience asked what it would look like if one were to create a similar animation of 40 million years into the future. Elam suggested that one would see the Farallon plate continue moving deeper into Washington and Oregon, and he explained that this subduction beneath the states is why there are volcanoes such as Mt. Saint Helens.

Elam explained why the San Andreas fault should be a subject of interest. In its more recent history, it has caused earthquakes such as the 1906 San Francisco earthquake (which resulted in the infamous and devastating fires) and the 1989 Loma Prieta earthquake.

Additionally, California is “overdue” for another large earthquake; geologists make this claim because earthquakes of certain sizes in certain areas happen relatively periodically.

For the duration of the presentation, Elam showed images that were evidence of the fault and its activity, as well as other animations showing the movement caused by the plates causing the fault.

He also talked about the San Andreas Fault Observatory at-Depth, or SAFOD, which tries to associate certain geological activity as a “precursor” to a coming earthquake.

Elam gives similar presentations each month at the Buena Vista Museum, which are free to attend after paying the entrance fee to the museum.