Potato Stones and Thunder Eggs

Wildfires Impact Snowpack

Snowpack provides our water, especially in the American West. And new research shows wildfires may be affecting it. Snow accumulates in the mountains in winter, then melts in spring to fill rivers. As we’ve discussed in prior EarthDates, that runoff is critical to water supplies, for irrigation, fisheries and cities. Earlier melting, due to more winter rain, has brought spring floods. This can mean lower water supplies in summer and fall. Now wildfires have been shown to also promote earlier melting. For the past century, U.S. forestry policy has been to put out all wildfires, which has led to an accumulation of deadwood that could burn as fuel. Combine this with hot, dry “fire weather,” and more people now living in fire zones, who set more fires, and the result is more acres of Western forests burned each year. Scientists analyzing snowpack across Western mountains found that an evergreen forest canopy reduces the amount of snow that can accumulate on the ground. But it reflects more sunlight from snow-covered branches. This keeps the ground cooler and slows melting. By contrast, where a forest has burned, more snow accumulates on the ground. But it reflects less sunlight, warms faster and melts as much as 10 days earlier in the season. More research is needed to understand how earlier melting in burned areas may affect runoff. But it could be another important tool for scientists analyzing water supplies in a parched American West.

Ancient Climate Control

Ancient heating and cooling systems operated without electricity, which could today provide solutions for climate control in places without electricity or where outages have become more common. Wind towers that capture wind or thick walls can work to passively cool or insulate buildings. Southern facing windows with shading devices, and adobe construction, can keep homes warm or cool depending on the season. Rainwater collection systems can store water through dry periods.

Potato Stones and Thunder Eggs

We’ve all seen geodes, and marveled at their beautiful crystal interiors, but do you know how they form? Geodes occur mostly in lava and sedimentary rocks. In molten lava, gas bubbles and lava tubes form, some quite large. They become voids as the rock hardens, and can fill with mineral-rich fluids. Over many years, minerals precipitate out, and crystals line the void. As more fluids seep in, more crystals grow. Geodes that form in lava often contain quartz crystals, especially amethyst, which is quartz colored purple by iron impurities. In sedimentary rock, pockets of mineral-rich water can crystallize in a similar fashion, sometimes with a translucent silica called chalcedony. When the sediment layers erode, geodes tumble out. The English call them “potato stones” for their telltale shape. Because they’re often partially hollow, you can tell by weight that they may contain a geode. Those that fill completely with silica are called thunder eggs. The world’s largest geode, as long as a school bus and tall enough to stand in, was found 20 years ago in Spain. If you’d like to find your own potato stone or thunder egg, look for outcrops or road cuts on public land, take a shovel to sort through the eroded rubble – and look where others have found them before. You may not find a world-record goliath, but you’ll enjoy the geologic Easter egg hunt!

Mystery of the Wallace Line

The Wallace Line, a boundary separating the unique species of Australia from those of Southeast Asia, has long fascinated scientists. Exploring the influence of plate tectonics, glacial periods, and geographic isolation may hold the answer to this mystery.

The Wood Age

For 99% of hominin history, we were living in the Stone Age. It began some 3 million years ago, followed much later by the Bronze and Iron Ages, at just 10,000 and 5,000 years ago. Hominins have used wood throughout those ages. For all that time, you could say we’ve been in a Wood Age -- though scientists never officially named one. Wooden artifacts don’t often turn up in the archaeological record, because they decompose. Nonetheless, traces have been found. Some stone tools in East Africa, dating to around 1.5 million years ago, show residue of being attached to wooden handles. A wooden plank apparently polished by humans was dated to nearly a million years ago in Jordan. In Eurasia, wooden spears from more than 300,000 years ago were likely used for hunting or fishing. A recent find near Kalambo Falls, in today’s Zambia, revealed wood logs cut by stone tools to form a platform or shelter. At 476,000 years old, these are the earliest known examples of wooden construction. And wood is still widely used today. The average American uses two pounds of wood each day, mostly in packaging. Building the average American house requires two to three acres of forest! And nearly a billion people still burn wood for energy. Though we never had an official Wood Age, we’re definitely still in it