This Year On Earth

by Mary Hrovat

In 2018, Earth picked up about 40,000 metric tons of interplanetary material, mostly dust, much of it from comets. Earth lost around 96,250 metric tons of hydrogen and helium, the lightest elements, which escaped to outer space. Roughly 505,000 cubic kilometers of water fell on Earth’s surface as rain, snow, or other types of precipitation. Bristlecone pines, which can live for millennia, each gained perhaps a hundredth of an inch in diameter. Countless mayflies came and went. As of this writing, more than one hundred thirty-six million people were born in 2018, and more than fifty-seven million died.

Tidal interactions are very slowly increasing the distance between Earth and the moon, which ended 2018 about 3.8 centimeters further apart than they were at the beginning. As a consequence, Earth is now rotating slightly more slowly; the day is a tiny fraction of a second longer. Earth and the sun are also creeping apart, by around 1.5 centimeters per year, although the effect of tidal interactions is very small. Most of the change is due to changes in the sun’s gravitational pull as it converts some of its mass into energy by nuclear fusion.

The entire solar system traveled roughly 7.25 billion kilometers in its orbit about the center of the Milky Way. This vast distance, however, is only about 1/230,000,000th of the entire orbit.

In 2018, there were two lunar eclipses and three partial solar eclipses, each a step in the long gravitational dance making up the roughly 18-year saros cycle. During one saros cycle, eclipses with particular characteristics (partial, total, annular) and a specific Earth–Moon–Sun geometry occur in a predictable sequence; at the end, the whole thing starts again. This pattern has been repeating for much longer than humans have been around to see it.

I like knowing these bits of cosmic context because they link me to a larger world. I can echo the words of Ptolemy: “Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth.”


Earth’s surface is also changing, although its activity is influenced by more complex factors and is generally not as regular. The Atlantic Ocean widened by about 2.5 centimeters over the course of 2018 as the rift valley along the Mid-Atlantic Ridge expanded. This expansion added new material, in the form of magma rising to the seafloor, to the North American and Eurasian plates (North Atlantic) and the South American and African plates (South Atlantic). The East African Rift, at which one plate is splitting into two, also widened, by about 6 to 7 millimeters.

The end of 2018 will probably find the Himalayas more than a centimeter higher than they were at the beginning of the year. They’re being pushed up as the Indian plate, which likely moved about 67 millimeters this year, continues to plow into the Eurasian plate. In human history, we like to identify turning points, decisive moments at which everything changed. However, tiny events can have tremendous effects, good or bad, if there are enough of them or they go on for long enough.

Some of Earth’s geological changes are visible well within a human lifetime. From May through September, 2018, for example, the island of Hawaii gained about 3.5 square kilometers of new coastal land in the form of lava from Kilauea. Anak Krakatau (Child of Krakatoa) in the Sunda Strait in Indonesia erupted explosively in 2018. It appeared in 1930 in the caldera left behind after the 1883 eruption of Krakatoa, and every year it grows by about 6.8 meters. The Pacific Plate moved roughly 7 centimeters over the hot spot that created (and is still creating) the Hawaiian islands. The North American plate moved about 3.3 centimeters in a roughly southwestern direction over the Yellowstone hot spot.


Earth’s atmosphere and hydrosphere are also driven by factors more complex than gravity, including human behavior. They provide not a seemingly unchanging backdrop, like the solar system and the galaxy and the continents, but rather a series of more or less regular periodic changes, punctuated at times by extremes.

The precipitation that falls every year has always been unevenly distributed in both place and time, for example, but it’s usually fairly seasonal and more or less regular. As the planet warms, however, extreme events become more likely. According to one estimate, Hurricane Florence dropped 10 trillion gallons of water over the Carolinas in September, breaking rainfall records in many locations. Hurricane Lane was the wettest ever recorded in Hawaii. It was followed by Hurricane Olivia, which briefly made landfall over Maui and Lanai—the first tropical cyclone to do so in recorded history. Within a couple of weeks in May, two tropical cyclones struck the Mideast, traveling over a part of the Arabian Sea where they’re rare. Two powerful super-typhoons, Mangkhut and Yutu, struck parts of southeast Asia.

Parts of the western US faced drought and extreme heat in 2018. In fact, depending on how the term is defined, the American West may be experiencing a megadrought, which is a more severe and less common period of extreme dryness. The longer and more active wildfire season in the western US reflects these severely dry conditions.

Drought and heat affected Europe this year as well. The UK, Greece, and Sweden faced serious wildfires, and there were even wildfires north of the Arctic Circle. Hunger stones, hydrological markers in Central European rivers, became visible as the water level dropped. These stones were placed in rivers during previous droughts, some of them hundreds of years ago; their surfaces bear warnings from the past about the dire outcomes of such low streamflow.

Global carbon dioxide emissions in 2018 were the highest ever recorded. Carbon dioxide emissions from fossil fuel use and industry in 2018 are predicted to be approximately 37 metric gigatons. This is about 2.7% higher than the 2017 total, which in turn was about 1.6% higher than the 2016 total. According to a December 2018 report by the Global Carbon Project, “The peak in global emissions is not yet in sight.”


We’re in the midst of the Holocene extinction. It’s difficult to estimate how many species have gone extinct or the rate at which they’re going. We don’t have a complete inventory of every species on Earth, and we don’t always know right away when a known species has vanished. The current rate of species loss is estimated to be 1,000 to 10,000 times the natural background rate. Extinction events like this are very rare; depending on the definition, there have been 5 to 20 of them in the last 540 million years. Unlike any of the previous extinction events, this one is driven mainly by a single species: us.

It’s hard to know how to live with this knowledge. Years ago for Christmas someone gave me a copy of The History of Earth, by William K. Hartmann and Ron Miller. This was in some ways a life-changing book; it widened my view of the timescale of geological history in a most exhilarating way. I loved reading about how Earth has changed on vast scales of space and time, and seeing beautiful illustrations of very different past Earths. Again, with Ptolemy, I felt expanded beyond my mortal self. However, I never expected to live within sight of one of those huge upheavals, climate change accompanied by an extinction event, and to have to come to terms with the fact that my species is the primary cause of it.

As I’ve grown older, I’ve learned to cope with loss by focusing on continuity, on what remains. But now I wonder if we humans can survive the damage we’re causing, and if we do, how we’ll live in the diminished world that we’re creating. The only meaningful continuity seems to lie outside of human concerns entirely, even outside of this beloved planet. (Of course, in the long run, it always has, but I never expected the long run to be potentially so short.) I’ve been trying on the perspective of Robinson Jeffers, who recommended that we see beyond humankind, and love, perhaps even identify with, the entire universe. This is from his 1937 poem “The Answer”:

Integrity is wholeness,
the greatest beauty is
Organic wholeness, the wholeness of life and things, the divine beauty
of the universe. Love that, not man
Apart from that, or else you will share man’s pitiful confusions,
or drown in despair when his days darken.

Is it going to be enough, to take comfort in the fact that the gears of the universe will continue to turn regardless of what happens to us, that Earth will still dance the stately pavane of the eclipses with the moon and sun even if we’re not here to see them, that ultimately Earth will probably continue to support life, even if that life doesn’t include humans? I think it’s going to have to be.


Many of the numbers in the first two sections are estimates based on average annual data. The birth and death statistics in the first paragraph came from Worldometers.

Image courtesy of Pixabay.

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