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Shark Planet

Sharks have been so successful, for so much longer than so many other lifeforms, that you could call Earth the shark planet. They evolved over 400 million years ago, meaning they’re older than trees. They’re 6 times older than the North Star! And over a thousand times older than humans. They’ve survived all 5 known mass extinction events. Over that long, long period, they’ve diverged into hundreds of species and adapted to every marine environment from deep oceans to estuaries. And they’re magnificent creatures: sharks recover from injury and heal quickly. They almost never develop cancers or get heart disease. And they’re immune to infections. Some species, like the Greenland shark, can live more than 400 years. Sharks are essential to the health of Earth’s oceans, culling sick and weak fish and scavenging dead ones. But today, they’re in great danger. Sharks mature and reproduce slowly, so they don’t adapt quickly to environmental changes. While they’re highly efficient predators, they have almost no interest in humans—we’re not their natural prey. But they’re often killed by fishermen. And their numbers are declining from overfishing, mostly for shark fin soup. Eighty million are caught each year, often their fins cut off while alive, then they’re thrown back to die. Instead of killing them, we should admire and protect one of Earth’s oldest and most well-adapted animals.

Plants Can Dance

You might think that plants are stationary, but did you know they can dance? Many flowers do a daily sun dance, swinging from east to west, to produce more pollen and attract insect pollinators. They make this movement using two methods: Plants contain a compound called phototropin that responds to being in shadow by causing cells to elongate. In this way, the dark side of the plant grows longer, which curves the other slower-growing side toward the light. All plants do this, but the sunflower is special. It can elongate its cells every minute! Each day as the Sun moves westward, cells on the east side of the stem just beneath the flower grow, tilting the flowerhead westward to follow the Sun. At night, the west side grows, pushing the flower back toward the east to greet the morning sun. The sunflower will do this daily dance until fully mature, when it stops growing, usually with the head facing east. Other plants in the sunflower family, like daisies and dandelions, can also follow the Sun, but use a different method. They pump potassium and water across cell membranes to inflate or deflate cells, thereby bending the stem. Using these methods, many plants can change their orientation, not only to light, but moisture, gravity and other stimuli. Not exactly dancing, but moving in rhythm more than we might think.

Pompeii: The Destruction

For millennia, people have been drawn to volcanoes. Why? Because before they arrived, the volcanoes had erupted. Their lava, ash and debris covered the surrounding area, making for fertile farmlands that drew settlers … who may not have recognized that the volcanoes could erupt again. And that’s just what happened around Italy’s Mount Vesuvius. Long before the Romans, people had come to farm there. When Rome eventually controlled the region, inspired by the pleasant climate and bountiful agriculture, they named it Campania Felix—the happy, fertile countryside. One of the happiest towns was Pompeii, a popular vacation spot of the day. But Mount Vesuvius would change all that. In AD 62, it sent earthquakes through the region, displacing residents. Most had returned when, 17 years later, Vesuvius erupted. First, it blasted a spire of ash and pumice 10 miles into the sky. This rained down on Pompeii, leaving a layer 8 feet thick. Most citizens fled, but 2,000 remained, sheltering in stone houses and cellars. The next day, clouds of burning hot toxic gas flowed down the mountain, instantly suffocating residents. More ash rained down, encasing the victims in their final positions. Their tragic end, however, would be a great boon to historians centuries later – which we’ll discuss in the next EarthDate.

More Auroras

Every 11 years, the Sun cycles from solar minimum to solar maximum, as we discussed in a prior EarthDate. And we’ve just entered another solar maximum, where the Sun emits many more charged particles in a faster, stronger solar wind moving toward Earth. You might experience it in disrupted GPS or cellular signals. But you can see it in the night sky. Specifically, in the aurora borealis, the famous northern lights. You may remember, also from a prior episode, that Earth’s magnetic field shields us from the charged particles in the solar wind, allowing life on Earth. Some particles still get through but are directed by the magnetic field around Earth toward its magnetic poles. These particles excite atoms in the atmosphere, which emit light. Oxygen emits mostly green light, and nitrogen red. They blend together in unusual ways to create many colors including blue, purple and pink. With stronger solar winds, more charged particles will get through, meaning brighter auroras that will be more visible, even at lower latitudes like the Midwest United States. But they’ll still be the most visible within 30 degrees of the magnetic poles, when the pole is farthest from the Sun, around midnight. And particularly around the spring and autumn equinox. So for your best shot at a spectacular nighttime light show, head to the Arctic Circle in mid-September. Maybe I’ll see you there.

Deep Ocean Drilling

For nearly 60 years, an international deep ocean drilling program has revolutionized earth science and understanding. Two research ships in particular, the Glomar Challenger, later replaced by the JOIDES Resolution, have drilled hundreds of miles of ocean sediment core, in every ocean. These cores provide a record of Earth stretching back millions of years. They’ve allowed scientists to validate the theory of plate tectonics, study ancient sea creatures, climate and sea level fluctuations, past earthquakes, volcanoes, asteroid impacts, changes in Earth’s magnetic field and more. And they’ve furthered science in monumental ways. They’ve helped us build the geologic time scale. Make the link between natural orbital cycles and long-term climate variability. Map global ocean circulation patterns to better understand how they warm continents and influence weather. They’ve shown us that the Mediterranean Sea has completely dried out, several times, and that the Arctic was once subtropical, abounding with warm-water life forms. They’ve discovered frozen natural gas beneath the seafloor, along with the sunken continent of Zealandia. In September 2024, the Resolution will be retired, after almost 40 years of service. Smaller European and Japanese ships will keep on drilling, while hopefully the U.S. builds another flagship, to continue the scientific discovery vital to human progress.