This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Tuesday, October 29, 2013

Huge MegaWave off the coast of Portugal: video

Big wave of October 28, 2013 from Surfertoday.com
This wave is at the so-called Nazare North Canyon (Praia do Norte) Portugal

The news has been full of reports about the big storm that battered England and northern Europe the past few days. News is just coming out about surfers catching the big waves generated by the storm. In the photo above, the two men pictured are competitors in the goal of surfing the world's largest wave. In January, less than a  year ago, Garret McNamara (left in photo) surfed what was believed to be the biggest wave to date then, about 100 feet high. He had previously ridden a 78' high wave in 2011. Carlos Burle, right above, may have topped that record with his ride on a 100" high or greater wave on Monday. A video is here, and one with more wave mechanics is here. The official height of this wave hasn't yet been announced, but speculation is that it may be a new world record.
           What generates such waves? In my book "The Dynamics of Disaster" published last week by W.W. Norton Press, I have a chapter on ocean waves, and specifically on rogue waves. I'll highlight a few points here: What is a rogue wave? What happens as they approach shore?
            Rogue waves are quite ephemeral, and that has made scientific documentation difficult. In 1861, a wave broke glass windows 85 feet above the ground in an English lighthouse--after climbing up a 130-foot high cliff! This would imply that the wave was 215 feet high, but as of now, no wave near this height has been documented by eyewitnesses or with instruments. Rogue waves are generated by storms, and they are a danger to  shipping, fishing, tourism, and oil and gas production on the ocean.
           Here's a quoted footnote from my book that defines rogue waves: "To provide a reference for defining rogue waves, oceanographers have introduced the concept of a “significant wave height.” The significant wave height is the average wave height of the one-third highest waves in a time period (typically taken as 10-30 minutes). Surfers might find the following exercise useful--and sobering: ignoring the small stuff, sit on a beach and make a list of the heights of all incoming waves for 10-30 minutes. For example, 1 foot (1’), 2 feet (2’), 3’, 5’, 3’, 4’, etc. Organize this list from biggest to smallest: 5’, 4’, 3’, 3, ’2’, 1.’ Keep the highest one-third of the values, 5’ and 4’. Then, take their average--4.5.’ This is the significant wave height. A rogue wave is defined as one whose height is two or more times the significant wave height--9’ in this example. In fact, rogue waves with a height more than four times the significant wave height have been documented. In this example, that would be an 18’-high wave. Surfers who are comfortable with 2’ or 3’ foot waves, perhaps an occasional 5’ wave, but not with 9’ or 18’ waves need to be aware that such waves can appear at any time. This is apparently what happened when a wall of water collapsed on and killed the experienced big wave surfer, Sion Milosky, at Half Moon Bay, California, in March, 2011. After nearly an hour of relatively small swells (18-20’) for that day, a rogue wave “bomb” rolled him to the bottom, where he was held down not only by this wave, but by a second as well, in what is known as a “two wave hold down” in surfing jargon. He was found too late, 20 minutes later."
Map showing the likelihood of encountering
a rogue wave within any 24-hour period.
Courtesy Burkard Baschek
     (Sorry, but I'm not doing well at controlling line spacing in Blogger if this looks wierd)

Broad patterns of wind and ocean currents determine the zones of hazardous rogue waves on the ocean (as discussed more broadly in the book). Four factors can operate simultaneously to determine the height of he waves on the open ocean and near-shore: winds from hurricanes and storms that churn up the ocean surface; the interaction of strong waves moving in opposite directions, such as storm waves interacting with strong oceanic currents or strong opposing winds; constructive interference (addition of wave heights) of random waves; and piling up of waves from the deep ocean into shallow depths along the continental shelves. See book for details! And, it's that last effect that makes surfing so exciting!

Monday, October 21, 2013

Megafires: The New Norm

Sydney skyline with smoke. Photo is from cnn.com here.
Photographer is Gregg Wood/Getty Images
Fire is raging outside of Sydney, Australia, and today firefighters are saying that the hoped-for rain is not coming. They now fear that the 50+ individual fires will join to form a "megafire." NPR.com did a 5-part series titled "Megafires: The New Normal for the Southwest"last year (August, 2012) and you can link to it here. This summary is taken largely from that article plus some other references. The weather is dry, lightning abounds, and the last winter was very dry providing lots of fuel. The fires have already burned an area the size of Los Angeles.
     Fires are a natural part of ecosystems like those in the American Southwest and Australia. For a hundred years, the U.S. Forest Service had a policy of fire suppression that resulted in the accumulation of a large amount of brush. I'm not sure about the Australian fire suppression policies. However, because Australia sees cycles of droughts and floods, large fires have been a prominent part of the ecosystem evolution.
     In the Southwest, up until about 20 years ago forests had as many as 50 times the natural density of trees--typically, Ponderosa Pines (the ones whose bark smells like vanilla on a sunny day!). The forests resembled a thicket of giant toothpicks with mops of green hair on top. This was a result of the fire suppression policies. The Forest Service realized the problem that it had created and began to try to thin the trees by letting naturally started fires (e.g., those started by lightning strikes) burn when structures weren't endangered. They also started prescribed burns on days when wind conditions permitted this to be done safely. Such fires clear out the undergrowth.  However, people don't like smoke from such fires, and when the occasional one got out of control, the Forest Service was subjected to law suits and so they burns were cut back.
     Firefighters are now being quoted in the press as saying that the megafires are something new, that they've fought big fires before but nothing like these.  According to Thomas Swetnam, a tree ring expert at the University of Arizona, old trees show scars of fires that burned them, but didn't kill them. Back in the 1600's such fires occurred about every 5-10 years--small grass and shrub fires that left the big Ponderosas and Doug firs alive. But then "around 1890-1900 the record stops--the "Smokey Bear effect."What happened? The Civil War had ended, Reconstruction was nearly finished, and the Manifest Destiny doctrine resulted in the westward expansion. Settlers brought livestock that ate the grass, so fires had little fuel. Then the U.S. Forest Service was formed and, as Swetnam says, "its marching orders were 'no fires.'"Expert wisdom was wrong. (You can see a time-laps series over 88 years showing changes in a forest landscape here.)
     The result was a Southwest with forests packed with trees, shrubs and grass--fuel. When fires start in forests with these conditions, the immense heat that they generate actually precooks fuel in front of an advancing fire by drying it out.
    There are, broadly, three types of fires (this classification comes from the U.S. Forest Service and is specifically for conifer forests, but general enough to apply here): ground or subsurface fires; surface fires; and crown fires. Ground or subsurface fires spread slowly without visible flames. Surface fires can spread with the wind or upslope (so-called "heading surface fires") or into the wind or downslope (so-called "backing surface fires.") Crown fires advance both through the tree tops and through over the surface. The transition from a surface fire to a crown fire is a significant escalation in the fire intensity, particularly because convection increases allowing embers to be spread far away from the initial fire. Three types of fires are shown in the figure below (taken from the USFS report referenced above).

   Forest fire fighters have developed various ways to try to anticipate fire conditions. Van Wagner (see the USFS report mentioned above) hypothesized that the type of crown fire to be expected in a conifer forest on any given day depended on three properties of the canopy fuel layer and two basic fire behavior characteristics. The Fire characteristics are the initial surface fire intensity and the rate of fire spread after the onset of crown combustion. The three properties of the canopy are the foliar moisture content, the canopy base height, and the canopy bulk density. The initial surface fire intensity, the foliar moisture content and the canopy base height determine whether or not the fire will ignite the foliage of the conifer, and the canopy bulk density and the rate of fire spread after crown combustion determine whether the fire can be sustained in the canopy.  The initial surface fire intensity and rate of fire spread in turn depend on windspeed, slope steepness, fuel dryness, air temperature, relative humidity and fuel characteristics. Models such as these are put together in various graphs to illustrate fire potential.
Van Wagner's diagram for fire classification
     Wagner's graph is illustrated here. The abbreviations are: Rate of spreading (ROS) and critical rate of spreading (ROScritical) and Surface fire intensity (SFI) and critical surface fire intensity (SFIcritical). The trap shows that if the surface fire intensity is low, then there is no crowning, only surface fire. If the surface fire intensity is high, then crown fires develop. They are either passive (if the ROS is low) or active (if ROS is high).

Saturday, October 12, 2013

Tropical Storm Phailin (Phailin means sapphire in Thai)

Projected route for Phalin from Accuweather.com
at this link
Today another superstorm has attacked India from the Bay of Bengal: Tropic Cyclone Phailin has hit northeastern India. Hundreds of thousands are either fleeing or being forcefully evacuated. Winds over 100 mph, and flooding in excess of 8" are expected, along with storm surges of up to 20 feet near the shore where landfall occurred.   Winds were in excess of 125 mph at the point of landfall at Golpalpur. The US Navy's Joint Typhoon Warning Centre predicted that Phallin could produce gusts up to 184 miles per hour.

Phailin and related geography
From The Weather Channe
In 1999, Cyclone Odisha struck and estimates are that up to 15,000 were killed. Up to this date, Odisha was the strongest tropical cyclone ever recorded in the Indian Ocean, and was the deadliest since a cyclone hit Bangladesh in 1991. It was a category 5 storm and followed a category 4 storm in the same general area by only a few weeks. Tens of thousands fled. The storm surge was 26 feet and it traveled up to 20 km inland.Nearly 7,000 square miles of crops and 90 million trees were destroyed. Nearly 1.7 million people were left homeless. Estimates are that up to 45,000 people died, but the official count stood around 10,000. Many people died of starvation and disease after the storm.

Since Odisha, authorities have vowed to reduce deaths and enforce mandatory evacuations. The area encompassed by the cyclone is home to millions of people. Most live in mud and thatch houses. The army is on standby and helicopters and food packages are being prepared for relief operations.

I have discussed hurricanes and cyclones in a number of other posts (see, for example, here; you can search the blog for others), so here are a few new facts (from the Hindustan Times reference given below).

In contrast to naming of hurricanes in the Atlantic, starting in 1979 cyclones in the Northwest Pacific are named in very different ways. By and large, personal names are not used. The majority of names refer to flowers, animals, birds, trees, or even foods, and some are descriptive adjectives. The names are selected by contributing nation, with the selection being from a list of the countries in alphabetical order.

I've been asked whether any good ever comes of disasters, and hopefully, the Indian's response to this one will be an example. In 1999, only tens of thousands were evacuated from this same area. This time it is hundreds of thousands. Let thoughts and prayers for success in their efforts fly across the ocean to those in the path of Phailin.

Here are more links:
Hindustan Times