The December Skies

During the first week in December, look for Mercury low in the southeastern morning twilight. It will sink lower in the sky each morning and will disappear into the solar glare.

Venus is fairly high in the southwest evening twilight as December begins but drops lower each day throughout the month.

Mars rises after midnight and is high in the southern sky at dawn. Because of its great distance, the Red Planet remains disappointing in a telescope.

Mighty Jupiter rises in the east-northeast evening sky and is easy to locate because of its brilliance. Its Great Red Spot is a high-pressure region that is big enough to hold two Earths.

Saturn rises in the east-southeast during the predawn hours and is fairly high at sunrise. Because of its rapid rotation, Saturn is visibly flattened at its poles when viewed through a small telescope.

The Geminid Meteor Shower peaks on the night of Dec. 13-14. However, this year a waxing gibbous moon will drown out the fainter meteors. The best time to observe will be between midnight and dawn.

The sun arrives at the Winter Solstice on Dec. 21 at 12:11 p.m. EST. This marks the beginning of winter in the Northern Hemisphere and summer south of the equator.

EARTH’S RING OF FIRE

“The safest place to be during an earthquake would be in a stationary store.”

– George Carlin

Our home planet can be a place of serene beauty with tranquil vistas, pleasant temperatures and soft breezes. But that peaceful scene can change in a fraction of a second when the ground beneath our feet shakes violently during a terrifying earthquake. When the usually solid ground begins to heave up and down and structures start to collapse all around you, it is one of the scariest natural disasters one can experience. As a survivor of the most powerful (magnitude 9.2) recorded earthquake in U.S. and North American history and the second most powerful ever recorded in the world, I write from experience. While serving with the U.S. Air Force in Alaska, the 1964 Good Friday Earthquake struck with such force that the entire planet vibrated and minor effects were recorded worldwide. Long period seismic waves traveled around the Earth for several weeks following the quake.

Scientists now realize that the surface of the Earth is broken up into about a dozen very large shifting plates or slabs that average about 50-100 miles in thickness. These rigid plates move in different directions very slowly in relation to each other over time, at about the speed your fingernails grow. Beneath these crustal plates, churning rivers of molten rock in the Earth’s mantle, heated by radioactive decay even further down, keep the plates moving in slow motion.

Most of our planet’s volcanoes and earthquakes occur along the margins of these tectonic plates. As the plates move in relation to each other, tremendous stresses can build up over many hundreds or thousands of years. When the rock breaks suddenly, the stored elastic energy is released as an earthquake.

Around the edges of the Pacific Ocean lies a horseshoe-shaped string of 452 volcanoes and numerous sites of seismic activity. This unstable zone stretches from the southern tip of South America, up along the western coast of North America, crosses the Bering Strait, then runs down through Japan to southern New Zealand. This vast arc is called the Ring of Fire and is home to most of the Earth’s active volcanoes.

The edges of several tectonic plates meet along this Ring of Fire, slowly spreading apart, sliding past each other, or colliding into each other. Scientists have evidence that the slow motions of these enormous plates have been occurring for at least the past 2,500 million years. They predict that this motion, if continued for another 50 million years, will imperceptibly push Australia into China, crushing all the islands of Indonesia and the Philippines into a mountain ridge between the colliding continents.

In general, our planet is and always has been a dynamic and many times violent sphere, ever since its formation 4.5 billion years ago. Very early in its history Earth was a lava world and it is still cooling to this day. Ever since the continents first formed, they have constantly shifted in relation to each other, with mountain ranges, islands, and seas forming and then eroding away over the eons. We can certainly expect additional devastating volcanoes, earthquakes and cosmic impacts in our future.

Editor’s note: This monthly guide to the stars is from the Marshall Martz Memorial Astronomical Association and The Post-Journal. For further information, contact the M.M.M.A.A. at www.martzobservatory.org