Elegant Earth : Alien worlds may be all the rage, with their mystique and promise, but the orb we call home, planet Earth, has all the makings for a jaw-dropping blockbuster movie from the drama of explosive volcanoes, past meteor crashes and catastrophic collisions between rocky plates to the seeming fantasy of the ocean's deep abysses swirling with odd life and tales of the coldest, hottest, deepest, highest and all-out extreme spots.
-Did you know Earth is not actually a sphere? That we are rocketing around the sun at 67,000 mph? That the majority of Earth's fresh water is locked up in Antarctica? Well, it's true !!
Our home, Earth, is the third planet from the sun and the only world known to support an atmosphere with free oxygen, oceans of liquid water on the surface and — the big one — life. Earth is one of the four terrestrial planet: Like Mercury, Venus and Mars, it is rocky at the surface.
Mother Earth has a generous waistline: At the equator, the circumference of the globe is 24,901 miles (40,075 kilometers). Bonus fact: At the equator, you would weigh less than if standing at one of the poles.
You may feel like you're standing still, but you're actually moving — fast. Depending on where you are on the globe, you could be spinning through space at just over 1,000 miles per hour. People on the equator move the fastest, while someone standing on the North or South pole would be perfectly still. (Imagine a basketball spinning on your finger. A random point on the ball's equator has farther to go in a single spin as a point near your finger. Thus, the point on the equator is moving faster.)
And, as you'll learn on the next slide, we're also racing around the sun at an incredible speed.
Oh yeah, and the Earth isn't just spinning: It's also moving around the sun at 67,000 miles (107,826 km) per hour.
Researchers calculate the age of the Earth by dating both the oldest rocks on the planet and meteorites that have been discovered on Earth (meteorites and Earth formed at the same time, when the solar system was forming). Their findings? Earth is about 4.54 billion years old.
(Photo shown here, what may be the oldest known rocks on Earth, called the Nuvvuagittuq Belt on the coast of the Hudson Bay in Northern Quebec, and dating back to 4.28 billion years ago, scientists estimate.)
Earth's moon looks rather dead and inactive. But in fact, moon-quakes, or "earthquakes" on the moon, keep things just a bit shook up. Quakes on the moon are less common and less intense than those that shake Earth.
According to USGS scientists, moon-quakes seem to be related to tidal stresses associated with the varying distance between the Earth and moon. Moon quakes also tend to occur at great depths, about midway between the lunar surface and its center.
As of March 2016, the largest earthquake to shake the United States was a magnitude-9.2 temblor that struck Prince William Sound, Alaska, on Good Friday, March 28, 1964. (Photos shows the Four Seasons Apartments in Anchorage, a six-story lift-slab reinforced concrete building, which cracked to the ground during the quake.) And the world's largest earthquake was a magnitude 9.5 in Chile on May 22, 1960, according to the U.S. Geological Survey (USGS).
The fiery award for Earth’s hottest spot goes to El Azizia, Libya, where temperature records from weather stations reveal it hit 136 degrees Fahrenheit (57.8 degrees Celsius) on Sept. 13, 1922, according to NASA Earth Observatory. There have likely been hotter locations beyond the network of weather stations. (The image was created from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite.)
It may come as no surprise that the coldest place on Earth can be found in Antarctica, but the chill factor is somewhat unbelievable. Winter temperatures there can drop below minus 100 degrees F (minus 73 degrees C).
The lowest temperature ever recorded on Earth came from Russia's Vostok Station, where records show the air plunged to a bone-chilling minus 128.6 degrees F (minus 89.2 degrees C) on July 21,1983, according to the USGS.
The southern continent is a place of extremes, with the Antarctic ice cap containing some 70 percent of Earth's fresh water and about 90 percent of its ice, even though it is only the fifth largest continent.
Did you know Antarctica is actually considered a desert? Inner regions get just 2 inches (50 millimeters) of precipitation a year (typically as snow, of course).
Spelunkers ahoy! The largest confirmed stalagmite in the world can be found in Cuba in the Cuevo San Martin Infierno. This behemoth rises 220 feet (67.2 meters) tall. (Shown here, a photo of a stalagmite in a northwest Yucatan peninsula cave.)
Because our globe isn't a perfect sphere, its mass is distributed unevenly. And uneven mass means slightly uneven gravity.
One mysterious gravitational anomaly is in the Hudson Bay of Canada (shown above). This area has lower gravity than other regions, and a 2007 study finds that now-melted glaciers are to blame.
The ice that once cloaked the area during the last ice age has long since melted, but the Earth hasn't entirely snapped back from the burden. Since gravity over an area is proportional to the mass atop that region, and the glacier's imprint pushed aside some of the Earth's mass, gravity is a bit less strong in the ice sheet's imprint. The slight deformation of the crust explains 25 percent to 45 percent of the unusually low gravity; the rest may be explained by a downward drag caused the motion of magma in Earth's mantle (the layer just beneath the crust), researchers reported in the journal Science.
Earth has a magnetic field because of the ocean of hot, liquid metal that sloshes around its solid iron core, or that's what geophysicists are pretty certain is the cause. This flow of liquid creates electric currents, which, in turn, generate the magnetic field. Since the early 19th century, Earth's magnetic north pole has been creeping northward by more than 600 miles (1,100 kilometers), according to NASA scientists.
The rate of movement has increased, with the pole migrating northward at about 40 miles (64 km) per year currently, compared with the 10 miles (16 km) per year estimated in the 20th century.
Earth’s magnetic field also varies in strength, and recently it was found to be weakening.
In fact over the past 20 million years, our planet has settled into a pattern of a pole reversal about every 200,000 to 300,000 years; as of 2012, however, it has been more than twice that long since the last reversal.
These reversals aren't split-second flips, and instead occur over hundreds or thousands of years. During this lengthy stint, the magnetic poles start to wander away from the region around the spin poles (the axis around which our planet spins), and eventually end up switched around, according to Cornell University astronomers.
And the title for tallest mountain goes to … either Mount Everest or Mauna Kea. The summit of Mount Everest is higher above sea level than the summit of any other mountain, extending some 29,029 feet (8,848 meters) high. However, when measured from its true base to summit, Mauna Kea takes the prize, measuring a length of about 56,000 feet (17,170 m), according to the USGS. Here are some of Mauna Kea's detailed measurements: The highest point is 13,680 ft (4,170 m) above sea level; the flanks of Mauna Loa continue another 16,400 ft (5,000 m) below sea level to the seafloor; and the volcano's central portion has depressed the seafloor another 26,000 ft (8,000 m) in the shape of an inverted cone, reflecting the profile of the volcano above it.
Earth may once have had two moons. A teensy second moon — spanning about 750 miles (1,200 km) wide — may have orbited Earth before it catastrophically slammed into the other one. This titanic clash may explain why the two sides of the surviving lunar satellite are so different from each other, said scientists in the Aug. 4, 2011, issue of the journal Nature.
Full story here : http://www.space.com/12529-earth-2-moons-collision-moon-formation.html
Do We Still Have a Second Moon?
Some scientists claim Earth has two moons currently. According to researchers reporting in the Dec. 20, 2011, issue of the planetary science journal ICARUS, a space rock at least 3.3-meter (1-meter) wide orbits Earth at any given time. They're not always the same rock, but rather an ever-changing cast of "temporary moons," say the scientists. Their theoretical model posits that our planet's gravity captures asteroids as they pass near us on their way around the sun; when one of these space rocks gets drawn in, it typically makes three irregularly shaped swings around Earth, staying with us for about nine months before hurtling on its way. Full story here : http://www.livescience.com/33641-earth-moons-theorists.html
Rocks can walk on Earth, at least they do at the pancake-flat lakebed called Racetrack Playa in Death Valley. There, a perfect storm can move rocks sometimes weighing tens or hundreds of pounds. Most likely, ice-encrusted rocks get inundated by meltwater from the hills above the playa, according to NASA researchers. When everything's nice and slick, a stiff breeze kicks up, and whoosh, the rock is off.
On May 8, 1978, climbers Reinhold Messner and Peter Habeler became the first to summit Everest without the aid of oxygen. Messner described his feelings upon reaching the top like this: "I am nothing more than a single narrow gasping lung, floating over the mists and summits."
How low can you go? The deepest point on the ocean floor is 35,813 feet (10,916 meters) below sea level in the Mariana Trench. The lowest point on Earth not covered by ocean is 8,382 feet (2,555) meters below sea level, but good luck walking there: That spot is in the Bentley Subglacial Trench in Antarctica, buried under lots and lots of ice.
We're not kidding! In Cameroon and on the border of Rwanda and the Democratic Republic of the Congo there are three deadly lakes: Nyos, Monoun and Kivu. All three are crater lakes that sit above volcanic earth. Magma below the surface releases carbon dioxide into the lakes, resulting in a deep, carbon dioxide-rich layer right above the lakebed. That carbon dioxide can be released in an explosion, asphyxiating any passersby.
As the climate changes, glaciers are retreating and contributing to rising sea levels. It turns out that one particular glacier range is contributing a whopping 10 percent of all the meltwater in the world. That honor belongs to the Canadian Arctic, which lost a volume equivalent to 75 percent of Lake Erie between 2004 and 2009.
Thunder and lightning reveal our planet's fiercer side. A single stroke of lightning can heat the air to around 54,000 degrees Fahrenheit (30,000 degrees Celsius), according to educational website Windows to the Universe, causing the air to expand rapidly. That ballooning air creates a shock wave and ultimately a boom, better known as thunder.
Bonus fact: Did you know there are about 6,000 lightning flashes around the Earth every minute?
The oceans cover some 70 percent of Earth's surface, yet humans have only explored about 5 percent, meaning 95 percent of the planet's vast seas have never been seen.
And this is fascinating: Some 300 million years ago, there was just one continent, a massive supercontinent called Pangaea. And thus there was just one giant sea, called Panthalassa.
And these vast seas are rich, holding more than 20 million tons of gold. But don't grab your mining hat just yet, the metal is so dilute that each liter of seawater contains, on average, about 13 billionths of a gram of gold. Undissolved gold is also tucked away in rocks on the seafloor, and though there's not efficient way of getting at that precious metal, according to NOAA, if we could extract all of it, each person on Earth could have 9 pounds of the shiny stuff.
The Earth is approximately 93 million miles (150 million kilometers) from the sun. At this distance, it takes about 8 minutes and 19 seconds for sunlight to reach our planet.
While the shifting slabs of rocks called tectonic plates are unseen to us, some of their effects are monumental. Take the Himalayas, which stretch 1,800 miles (2,900 km) along the border between India and Tibet. This immense mountain range began to form between 40 million and 50 million years ago, when India and Eurasia, driven by plate movement, collided. The tectonic crash led to the jagged Himalayan peaks.
When we think about big life, whales and elephants come to mind. But try on this tree for size: The General Sherman giant sequoia is the largest known stem tree by volume on the planet. The trunk of the tree contains slightly more than 52,500 cubic feet (1,486.6 cubic meters) of material. (Shown here, Giant Forest, Sequoia National Park.)
Finally, there are almost surely more planets like ours. Space scientists have found evidence of Earth-like planets orbiting distant stars, including an alien planet called Kepler 22-b circling in the habitable zone of a star much like ours.
Whether any of these planets will harbor life is an open question.
Auroras occur when charged particles from the sun are funneled toward Earth by the planet's magnetic field and collide with the upper atmosphere near the poles. They are more active when the sun's activity peaks during its 11-year solar weather cycle.
The southern lights, also called aurora australis, are seen less often than aurora borealis, the northern lights, because few people brave Antarctica's dark, freezing winters. Shown here, a 2008 image taken from Antarctica of the dazzling sky lights.