Friday, November 23, 2012

Earthquakes and Climate Change - Related?

Here is another example of a bright student trying to put things together. Sometimes there are things that are big and in the same place - but are still unrelated:

I am training to become a teacher, and my professor wants us to become more familiar with supplemental resources, such as this website. So he has asked us to generate a question and submit it to you and then give him the answer we get back. I thank you in advance for your feedback! Question: Are earthquakes, like storms are said to be, tied to climate change? Can you explain why or why not? Thank you so much! 
-Sarah S

No, earthquakes are not tied to climate change, and the main reason is because of they are not coupled (or very poorly coupled): Other than very temporary shaking of the ground, which is connected very poorly with the atmosphere, the huge energies involved in earthquakes are generated in, released in, and remain below the Earth's surface. Permanent surface manifestations of earthquakes (cracks or displacements) are uncommon except for the largest events, and are generally small and limited in scope, at least in terms of the scope of weather fronts moving across the Earth.

For a long time earthquake scientists have tried to find an association between earthquakes and syzygy (Solar and Lunar tides), but the correlation is just not there. Nor is there any correlation between volcanic eruptions and tides. Weather *IS* correlated with the orientation of the Earth's axis of course: when the north pole is oriented towards the Sun in the northern hemisphere summer, there is different weather than with the opposite orientation. Hurricanes and typhoons occur between June and November in the northern hemisphere, and the timing appears to be a heat latency effect. It takes awhile for the summer solar heat to accumulate in the upper ocean realm (water has a high heat coefficient, so it takes awhile to warm it up), and hurricanes derive their energy from the heat in warm ocean water. Hurricane Sandy was an unusual late-season event, because of the way pressure fronts interacted with each other to drive the storm backwards from the usual trade wind tracks and onto the New Jersey coastline.

Weather also correlates with the amount of CO2 and methane in the atmosphere, and also with the amount of energy that the Sun produces, but the critical geological record on the latter is distant in time and thus difficult to resolve clearly (see Among scientists, the anthropogenic (human-caused) contribution to climate is now widely accepted as the evidence keeps piling up: the increasingly severe weather events of the past half century are caused in no small part by fossil fuel combustion. Of the hottest 10 years in the past century, 9 of them have been since 2000, and that correlates well with the growing levels of CO2 in the atmosphere. A good article to pursue this topic further is here:

Interestingly, methane is approximately 37 times more potent than CO2 as a greenhouse gas, and the amount of methane produced/converted by a single cow from the vegetation it eats is quite large. With the burgeoning human population and its increasing affluence, more people seek protein, and thus the number of meat-producing animals has skyrocketed in the past century. By itself this new methane is frightening. However, there is a huge amount of sequestered methane in what are called methane clathrates or methane hydrates - methane bound up in water ice beneath the ocean seafloors (see This methane remains stable (and sequestered) as long as the pressure and cold temperatures around them don't change. However, with increasing temperatures caused by global climate change, it appears that these clathrates could become unstable, freeing more methane into the atmosphere, which will then get hotter, freeing ever more methane in a potential runaway feedback cycle.

Welcome to the increasingly interesting 21st Century!

Tuesday, November 20, 2012

Earthquakes: How Often?

Until the following question arrived, I had only thought of earthquakes as being relatively localized features, mainly occurring along continental margins and ocean-floor spreading centers or transform faults. The San Andreas fault is a mostly on-land transform fault. I hadn't really thought about how MANY earthquakes there are in the world as a whole.

Hello, I was wondering how many earthquakes happen typically in a year?
-Lauren J


The USGS estimates that several million earthquakes occur in the world each year. Many go undetected because they hit remote areas or have very small magnitudes. The National Earthquake Information Center in Denver, CO, now locates about 50 earthquakes each day, or about 20,000 a year. There are far fewer large events than small earthquakes, and this website will show you how these are parsed out according to magnitude:

There are lots of fascinating stats here, including an interesting table (below). Like asteroid impacts and frequency, or volcanic eruption magnitude and frequency, these all seem to follow an inverse log law:
The bigger the event, the less common it is.

Frequency of Occurrence of Earthquakes

MagnitudeAverage Annually
8 and higher
7 - 7.915 
6 - 6.9134 
5 - 5.91319 
4 - 4.913,000
3 - 3.9130,000
2 - 2.91,300,000

Saturday, November 17, 2012

Extinctions: Asteroid Impacts vs. Volcanic Eruptions

The following question indicates that someone was thinking about things - a large step beyond just going to school and memorizing facts.

Hello, I am 20 years old and from Portugal. My question arose when studying for school and noticing that these two events happen, more or less if it can be said on this matter, at the same time. Can a major impact like the one at Chicxulub have enough power to send shock-waves trough the mantel causing the major eruption at the Deccan traps? like if you "squeezed" the Earth and at its weakest point it broke, or like when you give a very strong hit on the top of the bottle and the bottom breaks away because of the pressure and strength that traveled until it finds a blockage it has the power to break through ... We know that earthquakes can be felt thousands of miles away but what happens inside the earth on the mantel at that time? If this is correct where would one get proof?
-Diogo C


You have observed an interesting timing association that has intrigued geologists for a long time.

From Wikipedia ( The Deccan Traps formed at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 65 million years ago. This series of eruptions may have lasted less than 30,000 years in total. The original area covered by the lava flows is estimated to have been as large as 1.5 million km², approximately half the size of modern India. The Deccan Traps region was reduced to its current size by erosion and plate tectonics; the present area of directly observable lava flows is around 512,000 km2 (197,684 sq mi).

One website ( offers this observation: "Researchers have simulated the meteorite strike that caused the Chicxulub crater in Mexico, an impact 2 million times more powerful than a hydrogen bomb that many scientists believe triggered the mass extinction of the dinosaurs 65 million years ago. The team's rendering of the planet showed that the impact's seismic waves would be scattered and unfocused, resulting in less severe ground displacement, tsunamis, and seismic and volcanic activity than previously theorized. "

Also from Wikipedia ( is even more specific information about the source of the Deccan Traps: "A geological structure exists in the sea floor off the west coast of India that has been suggested as a possible impact crater, in this context called the Shiva crater. It has also been dated at approximately sixty-five million years ago, potentially matching the Deccan traps. The researchers claiming that this feature is an impact crater suggest that the impact may have been the triggering event for the Deccan Traps as well as contributing to the acceleration of the Indian plate in the early Paleogene. However, the current consensus in the Earth science community is that this feature is unlikely to be an actual impact crater."

The short answer is that the Deccan Traps probably did not cause the extinction that wiped out most of the non-avian dinosaurs, though it may have contributed to making life even more difficult. There appears to be no connection between the Deccan Traps and the Chicxulub event.

On a related tack, the even larger Siberian traps ( formed 250 million years ago, and may have contributed to or even caused the Great Dying, the Permian-Triassic extinction event, the most complete extinction event in Earth's history. More than 90% of all species living in the Permian era abruptly disappeared at this time.

Wednesday, November 14, 2012

Coral Reefs as Resources

The US Geological Survey expends a lot of time and manpower on resource estimation: energy, minerals, biological (in several ways). The following question came at me sideways, and caused me to really think.

What are some resources that coral reefs provide?
What are some topographical features around coral reefs?
- Maya R

The main resources that coral reefs provide - that most people talk about at least - is biodiversity. This is a hard thing to quantify or explain, but if reefs all die from acidification and heat related to climate change, then much of the food-chain in the oceans would be severely disrupted. Some new drugs have already been derived from unique reef species, so that is another potential future resource. I believe that there are some entities that have mined reefs for the calcium carbonate that they contain, but this is like the Spaniards four centuries ago melting down precious Aztec and Incan gold artifacts. Trying to capture a "resource" this way destroys 95% of its value.

Coral can only grow where there is light, so this generally means the fringe waters of islands and coastlines, and only in tropical latitudes. In the Pacific, this often means that there are reef rings around volcanic islands or below-the-surface guyots. As the original core rocks of the volcanic island weather and crumble down, this generally means that the remaining topographic feature is an atoll: a coral ring with a shallow lagoon inside. There is very little topographic relief above the water line. The topographic fall-off of an island reef system tends to be steep, however. I've Scuba-dived some of these and the reef "wall" looks like it just goes straight down into the black depths. There are also reef systems on continental margins, and the Great Barrier Reefs of Australia and Belize are examples. Bathymetry tends to follow this characterization as one moves outward: the continental margin, then shallow water, then a reef system, than a steep fall-off to the continental shelves or in some cases the oceanic abyssal plain.