Dynamic Earth: Earthquakes, Tsunamis, Supermoons, and Japan

Tsunami Wave
from National Geographic

Earthquakes occur all the time; look at the USGS list of earthquakes in the past 8-30 days. There are a few hundred entries, most around a magnitude of 4 or 5. The plates that make up the Earth's crust move about constantly, so these minor tremors are quite common. A 4 on the Richter scale is strong enough to be felt, but not strong enough to cause much concern or damage. There are a couple thousand of these a year. Anything less than a 4 is a microquake; these are too weak to be felt, and are only recorded on local seismometers. Anything more than a 7 or 8 is a "great" earthquake. These are far less common; usually, there are only one or two great earthquakes per year. These earthquakes are the ones that cause trouble when they hit populated areas.

The earthquake that hit Japan last Friday was undeniably a great earthquake. It ranks as a 9.0 on the Richter scale, making it the 4th largest earthquake to occur in the past century. It caused a lot of damage, and in some places moved the crust by as much at 8 inches. Like the strong Chilean earthquake a year ago, it also shifted the Earth's axis slightly, shortening the day by about 2 microseconds (source). It also triggered a massive tsunami that hit Japan, Hawaii, and the US west coast, causing even more damage. Currently, Japan is still on alert as the Fukushima nuclear power plant threatens meltdown from damaged caused by the quake and tsunami. Evelyn, one of the Skepchicks, has been following this crisis with her father, a nuclear engineer, and has some great information up at her Georneys blog. It was truly a devastating quake, and needs to be seen to be truly understood.




This is a major natural disaster, and Japan need support and assistance from the rest of the world. What they do not need are a lot of pseudoscience explaining why the earthquake occurred or how recovery efforts should be run. One of the first pieces of nonsense was the supermoon idea. On March 19th, the moon will be closer to the Earth than at any other point during the year, and will also be full. Some astrologists claimed that this would increase the tidal forces to the point where the continental plates moved. This is simply wrong. First off, no matter where the Moon is in its procession and cycle, the tidal forces aren't strong enough to cause anything more than a microearthquake, if that. Second, the quake did not occur on the supermoon day; it occurred a week before, where the Moon is not at the minimum distance from the Earth, and when it has the weakest tidal forces in the monthly cycle. There is simply no way that the Moon had any causal effect on last Friday's earthquake.

The second, somewhat disturbing, piece of pseudoscience is the homeopathic groups distributing their medicines for nuclear radiation. Homeopathy, for those that don't know, is the concept of diluting a substance repeatedly, supposedly increasing the strength of the remedy each time it is diluted. (Mad Art Lab did an excellent job of illustrating the idea.) How this works for radiation, I don't know. These groups are trying to help, but are doing so with nonsense, and will likely cause more harm than good.

If you want to help the recovery efforts, first educate yourself; there is a lot of information available, both good and bad. If someone makes a claim about a natural disaster, check science sources, such as the USGS Earthquake page, to find out the facts, and sites like ScienceDaily and LiveScience to find out what the experts are saying, without as much of a media spin. Searching skeptical sites is also a way to sort the wheat from the chaff. Then, look into how you can help. There are some other groups doing real work. Doctors Without Borders and the Red Cross both do very good work, and are engaged in Japan right now. These groups provide shelter, real medicine, food, and materials to those affected by the disaster.

The Census of Marine Life

Around 70% of Earth's surface is covered in water. On average, this water -the ocean- is about 14,000 ft (2.65 miles, 4.267 km) deep.^(source) The ocean is also one of the least well-explored places on our planet. It's practically an alien world. Recently, numerous scientists, including marine biologists, oceanographers, geologists, and others, have been working to rectify this gap in our knowledge of the planet. One exciting new step they've taken is the new Census of Marine Life.

The scale of this project was fantastic: over 2700 scientists, from more than 80 different countries, publishing 2600 papers over the course of a decade, spending countless hours on field expeditions and lab analysis. The recently published Census shows an impressive scale of oceanic diversity: 120,000 species, from plankton to whales and everything in between, were observed through the course of this project. Multiple maps were created to show where different organisms live.

Still, as impressive and large scale as this census of the oceans is, it's far from comprehensive. On the maps of organism ranges, there are places that show where the sea has yet to be explored. Dr. Ian Poiner, chair of the Census Steering Committee, claims that there are still at least 3/4 of a million species in our oceans that remain undiscovered. This is just a start to understanding our fellow creatures beneath the waves. There's a lot yet to learn. Space may be the final frontier, but the ocean holds tantilizing opportunities for exploration as well.

For more information on the Marine Life Census, and to explore the OBIS (Ocean Biogeographic Information System) database, visit the Census of Marine Life.

Source: Science Daily: First Census of Marine Life shows ocean life is richer, more connected, more altered than expected

Dynamic Earth: Tsumanis

When I first introduced plate tectonics, it sounded like a relatively boring force. It's kind of cool that the Earth's surface is made up of gigantic slabs, which move around and collide. But these slabs move at the same rate that fingernails grow. Even with the huge mass of each plate, you wouldn't expect things moving at 5 cm a year to do much. However, as demonstrated by earthquakes and some types of volcanoes, the slow-moving plates can have pretty devastating effects. Along with these, there's a third type of natural disaster often associated with plate tectonics. And this one comes by sea.

Tsunamis, also called tidal waves (although this is a misnomer) are some of the most impressive natural disasters, second only to volcanoes. They are a gigantic wave of water that crashes onto land. The 2004 tsunami in the Indian Ocean was over 50 ft tall (15 m) in some areas. This, like most tsunamis, was caused by an earthquake. A tsunami is basically a series of enormous ripples, when a large amount of water is displaced. In the deep ocean, tsunami waves are very small, barely enough to rock a boat. It is when they get to land that they become devastating. The column of water drags along the ocean bottom, while the top part continues to move quickly. This speed difference causes the tsunami to reach devastating heights. The animation below shows how this works.

Like I mentioned above, tsunamis are caused by displacement. Underwater earthquakes are the primary cause of these. However, large landslides into the ocean can also cause tsunamis. This occurred in Lituya Bay Alaska, in 1958 causing one of the largest tsunamis ever recorded. Geologists and oceanographers also predict that the next mega-tsunami will occur if volcanic activity causes a landslide in the Canary Islands. A good portion of the island would collapse into the ocean, sending a tsunami wave towards the east coast of the United States. Between that, and the Yellowstone caldera, there is not a lot of the United States that will be secure from natural disasters. Fortunately, these gigantic events are rare, and can be monitored using seismographs and other devices, so there will should be plenty of warning before a giant tsunami, or some other mega-disaster occurs.

Credits: NOAA, National Geographic, Extreme Science