True polar wander is a geophysical theory, a way of thinking about Earth processes that might happen and that these scientists believe do happen. The theory suggests that if an object of sufficient weight on Earth – for example, a supersized volcano or other weighty land mass – formed far from Earth’s equator, the force of Earth’s rotation would gradually pull the object away from the axis around which Earth spins. A supersized volcano far from Earth’s equator would create an imbalance, in other words. As explained at Princeton.edu: If the volcanoes, land and other masses that exist within the spinning Earth ever became sufficiently imbalanced, the planet would tilt and rotate itself until this extra weight was relocated to a point along the equator. That’s the theory of true polar wander. It would cause a movement of Earth’s land masses, but for a different reason than the reason the continents drift in the theory of plate tectonics (formerly called “continental drift”). In the theory of plate tectonics, the continents drift because Earth’s the layer of Earth underlying our planet’s crust (called the mantle) is convective. That is, it circulates, slowly – like water about to boil. In true polar wander, on the other hand, a similar-seeming movement of land masses on Earth’s crust happens in order to correct an imbalance of weight with respect to Earth’s spin. Scientists’ understanding of true polar wander overlaps with their understanding of plate tectonics in various ways. That’s understandable, since it’s all the same Earth. Scientists delving into true polar wander want to know when, in which direction, and at what rate the Earth’s solid exterior might be rotating due to true polar wander. To sort it out, they say, you would need a stable frame of reference to which observations of relative motion might be compared. Doubrovine and his team say they found one: volcanic hotspots. Oceanic hotspots form an island chain. As land plates drift, a successive of volcanoes form over the hotspot. In geology, hotspots are volcanic regions fed by Earth’s underlying mantle. For example, the Hawaiian Islands are believed to have formed over a hotspot in the mantle. The hotspot created a volcano, but then – as that land plate drifted over time, as described by the theory of plate tectonics – the volcano drifted, too, and was eventually cut off from the hotspot. Gradually, another volcano begins to form over the hotspot, right next to the first one. And then it moves on … and another one forms … and so on … and so on. Earth’s crust produces first one, then another volcano over the hotspot until a long chain of volcanoes forms, such as in Hawaii. Hotspots have long been used to understand the motion of tectonic plates. Doubrovine and colleagues went a step further in order to understand true polar wander. Instead of treating the hot spots as static – frozen in place at one spot above Earth’s mantle – their computer model let the hotspots’ positions drift slowly. According to these scientists, this drifting is what produced a model of a stable reference frame, which in turn let them draw conclusions about true polar wander. They say their model does a good job of matching observations of real hotspot tracks on Earth – the path drawn by each hotspot’s island chain – which gives them confidence their results about true polar wander are accurate. –Earth Sky
That’s the sound of the Earth “singing,” as recorded by the awesomely-named Storm Probe mission — a couple of satellites investigating the famous Van Allen belts, intense radiation zones that surround our planet like a doughnut. The Storm Probes, launched last month, are mapping the density of charged particles.
The whale song is an audio rendering of radio waves captured by the Probes and caused by the two Van Allen belts, inner and outer. You don’t actually hear the audio in space, of course, but the radio waves — known as “chorus” — are for real.
Ham radio operators have been hearing chorus in the background for years, but there’s never been a recording this clear. “Our data is sampled at 16 bits, the same as a CD, which has not been done before in the radiation belts,” says mission scientist Dave Sibeck. “This makes the data very high quality and shows that our instrument is very, very healthy.”
The instruments may be, but chorus isn’t. The soothing radio waves are used by loose electrons to gain energy, much like a surfer gaining speed on real waves — creating what NASA calls “killer electrons” that can harm humans and electronics.
Sibek’s next goal: use the two spacecraft in tandem to create a stereo recording of chorus. That should make for a truly killer sound.
Guatemala is evacuating tens of thousands of people after the Fuego volcano started spewing ash and lava.
Volcanologists said powerful eruptions were catapulting burning rocks as high as 1,000m (3,280ft) above the crater and lava was flowing down its slopes.
Locals reported how the roaring of the volcano shook windows and roofs in nearby villages.
Experts say the eruption of the Fuego, 50km (31 miles) south-west of Guatemala City, is the biggest since 1999.
Head of Emergency Evacuations Sergio Cabanas told the Associated Press news agency that more than 33,000 people were being evacuated.
Officials from the National Institute of Seismology, Volcanology, Meteorology and Hydrology (Insivumeh) said lava was covering a 7km (4.3-mile) area on the south and south-western side of the Fuego.
The authorities recommended that air traffic controllers suspend flights in the vicinity of the volcano, as the ash cloud emanating from its crater was spreading quickly.
The 3,760m-tall (12,336ft) Fuego is one of Central America’s most active volcanoes, according to the Smithsonian Institute’s Global Volcanism Program.