The Heartbeat of the Planet


Checking a person’s pulse is a way to know that the person is alive or how fast their heart is beating. A normal resting heart rate for adults ranges from 60 to 100 beats per minute. Generally, a lower heart rate at rest implies more efficient heart function and better cardiovascular fitness. For example, a well-trained athlete might have a normal resting heart rate closer to 40 beats per minute.

Every 26 seconds, the Earth pulses.

The Earth’s pulse is not enough that you can feel it. Seismologists in different places around the world have been measuring the pulses for decades, but they don’t know for sure what is causing it.  This pulse was first documented in the early 1960s.

In seismology, the term microseism is defined as a faint earth tremor caused by natural phenomena and it is sometimes referred to as a “hum.” According to Wikipedia, it should not be confused with the anomalous acoustic phenomenon of the same name. The term is most commonly used to refer to the dominant background seismic and electromagnetic noise signals on Earth, which are caused by water waves in the oceans and lakes.

Since then, digital seismometers have moved the research forward. It seems that it is strongest during storms but the pulse is constant. In 2005, Greg Bensen at the University of Colorado-Boulder noted a strong signal, coming from somewhere far off.  His team considered possible sources – instrument error, incorrect data analysis, or that this seismic activity was real. They were even able to triangulate the pulse to a single source in the Gulf of Guinea, off the western coast of Africa.

But is it caused by waves? Volcanic activity?

It’s interesting but not particularly shocking or new. There is seismic activity all the time, not just during an earthquake or volcanic eruption.

Another way to look at it is to point to the Sun which heats the Earth more at the equator than at the poles and creates winds and storms and ocean currents and waves. When a wave hits a coastline or the continental shelf, the energy is transferred to the land and the pressure deforms the ocean floor.

Other scientists still favor the volcanic explanation. The pulse’s origin point is close to a volcano on the island of São Tomé in the Bight of Bonny.

And other scientists say that why is the pulse there when there are other continental shelves and volcanoes around the world. Why aren’t there other pulses?

I like scientific studies that are still unsolved after more than a half-century. I like the mystery. And I like that the planet has a pulse.

If we look beyond our planet, astronomers think they’ve solved a cosmic mystery surrounding fast radio bursts – powerful emissions of radio waves in space. Astronomers believe they have been able to track a burst back to a type of dense star called a magnetar. Magnetars have more mass than our sun but are squeezed into an area about the size of Manhattan. They occasionally spew bursts of radio waves and that’s what’s been causing the mysterious phenomenon lately. The bursts aren’t dangerous to humans.

One theory before this was that it was an alien signal.  That one was less scientific but certainly more fun. It would really be exciting if the Earth’s pulse came from radio waves sent here by aliens. No one seems to be investigating that possibility though.

The Anthropocene and the Technium

The Earth at night lights up showing humankind’s influence on it.

Kevin Kelly has turned me on to a number of interesting ideas. He wrote on his blog about the arrival of a third geological era called the Anthropocene and he led me to think about new fossil cities.

The Anthropocene is an informal geologic chronological term. It was coined to mark the evidence and extent of human activities that have had a significant global impact on the Earth’s ecosystems. Ecologist Eugene F. Stoermer coined the term and since it has been popularized by the Nobel Prize-winning atmospheric chemist, Paul Crutzen. He considers the influence of human behavior on the Earth’s atmosphere in recent centuries as so significant as to constitute a new geological epoch for its lithosphere. But the term has not been adopted as part of the official nomenclature of the geological field of study.

Kelly coined his own term, the technium, in his book What Technology Wants as part of his explanation of how technology has altered the planet.

In it, he views technology as a natural system going through something similar to biological evolution. He believes that if we map the behavior of our technology, we can see where technology is headed, or as he terms it, “what technology wants.”

He does see that ultimately our megacities – built from metal, brick, glass and stone mined from the earth – will eventually return to the earth, to be reprocessed into new minerals.

Kelly also pointed me to Jan Zalasiewicz’s book, The Earth After Us: What Legacy Will Humans Leave in the Rocks  which looks at how all the products of the technium might one day be fossilized.

He is writing about a thought experiment one hundred million years into the future. It is long after the human race we know becomes extinct. If someone visits the Earth at that point and tries to piece together the brief but dramatic story of our time on Earth, what will they be able to decipher about the history of humanity from the traces we will leave in the rock strata?

What kind of fossils will humans leave behind? Cities, cars, plastic cups and bones will tell what story?

A New Island

Niijima (NASA)
Niijima (NASA)

The Earth is still changing geologically, even though we commonly think of all those changes as something from the distant past.  Mountains and oceans are being created and destroyed and almost nothing is permanent.  Our little human lifespan is short enough to not take notice.

So, it’s nice to have an occasional reminder – like when a volcano creates a new island.

Just a few days before our Thanksgiving, an eruption began in the Pacific Ocean about 600 miles south of Tokyo. In the weeks that followed, an island has formed.

People are calling the new land mass Niijima. It has an area of about 14 acres and it continues to grow.

Newly formed islands don’t only survive. They can quickly erode or the sea floor sinks under the weight of them and they go below the surface of the water. But, so far, Niijima is remaining an island as a reminder that life is change.

I hope Google doesn’t buy it.