The Earth Story

Moving mountains

The ability of a current to move rocks depends on a couple things; the speed the water is flowing at and the depth of the moving water. Deeper water moving faster has greater energy and is therefore able to move bigger pieces of sediment. Stronger waves move bigger sediment. The strongest waves in deep water...they can move really big rocks.

Scientist Andrew Kennedy from the University of Notre Dame documented this boulder and several comparable monstrous chunks of rock that were moved onshore during the strike of Super-Typhoon Haiyan on the Philippines in 2014. . He described these as the largest rocks he’s ever seen moved by a storm, comparable in size to rocks picked up in the 2004 and 2011 tsunami waves.

-JBB

Image credit: Andrew Kennedy https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/5848

Read more http://www.livescience.com/49201-haiyan-waves-moved-giant-boulders.html

Slides This amazing image of a formerly forested slope was captured outside of Atsuma town on Hokkaido Island, Japan, after a major earthquake followed shortly after heavy rains from Typhoon Jebi. Loose sediment making up the slopes in this area, waterlogged and heavy after the rains, liquefied and collapsed downwards during the quake, taking huge numbers of trees along with. There’s a good chance you will never see more landslides in a single photo in your lifetime. Reportedly, basically all of Hokkaido Island lost electric service during the quake. About a dozen people are known to have died, with several dozen more missing as of last press reports. -JBB Image source: AAP http://bit.ly/2MWjO8L More: https://wapo.st/2wSk9hQ

Taiwanese Typhoons Trigger Turbidites

These sedimentary layers are turbidites, the remnant of ancient debris flows underwater. Turbidites are the main way that sediment deposited in the shallow water near a continent makes its way into the deep ocean. Rivers and streams bring sediment to the ocean and deposit it near the shore, and then eventually so much sediment is deposited near the shore that it becomes unstable and slides down to the deeper part of the ocean, often in submarine channels.

Turbidites can be recognized in sedimentary layers by what is known as the Bouma sequence – a classic pattern where the coarsest grained sediment is at the bottom and the sediment gets finer to the top. In this sequence, the big brown layers are sandy, while they thinner dark layers are silt to clay. These turbidites started as flows of sand and silt moving cascading down from shallow water to deep water. The heavier sand stayed at the bottom of the flow, forming the sandy layer, while the silt and clay were suspended above the flow and only settled out into layers after the flow stopped.

Scientists at Tongji University in Shanghai just published an interesting study regarding turbidites in Taiwan. Turbidites can be triggered by many things; weather on shore, earthquakes, or just random events. Over a 3.5 year period from 2013 to 2016, an area of Taiwan that feeds into a submarine canyon known as the Gaoping Canyon received heavy rainfall from 16 typhoons. The scientists tracked turbidites in this area and found that 72% of the sediment delivered to this canyon as turbidites occurred during these storms. While this is not the case everywhere, at that particular spot, typhoons are therefore the main trigger of sediment moving into the deeper ocean.

-JBB

Image credit: https://flic.kr/p/UgSo

Reference: http://bit.ly/2vhdm1f

New Land

This tiny island is Nadikdik Atoll (also called Knox Atoll) in the Marshall Islands of the Pacific Ocean. It is a coral island, one of many in the Pacific Ocean, and it has a wonderful story to tell.

Coral islands are found all over the Pacific whenever a seamount comes close to the ocean’s surface. Seamounts are often built by volcanoes and the rocks they erupt can be washed away by waves, leaving flat platforms just below the ocean surface where coral can grow. The coral will grow upwards along the edges of the seamount, building reefs like this one, which can on occasion breach the surface.

This little island is about 8 kilometers long, but its very presence is fascinating because in 1905 it was destroyed during a major typhoon.

Researchers from the University of Auckland wanted to track the recovery of this island. They found images of the island taken by the US Navy in 1945 and, combined with modern-day photos, they were able to track how the island recovered over the last 60 years.

A number of small, sandy islands along the reef which weren’t present in 1945 are there now. Others have expanded in area, others joined together, and still others have stabilized as trees and vegetation have grown. The islands also have migrated as they grow, even taking up the positions where islands sat prior to the typhoon.

This study shows that these islands are dynamic even in response to disaster. These islands were able to regrow after being destroyed since the reef survived and the sediment supplies weren’t changed. This research will have implications for the future as many of these low-lying Pacific islands are facing a future cataclysm due to sea-level rise. The good news might be…if these islands can recover and survive, maybe there are ways to stabilize or save other islands from their impending fate as well.

-JBB

Image credit: NASA http://dx.doi.org/10.1016/j.geomorph.2014.02.006

Maria

This is typhoon Maria, viewed from NASA’s Aqua Satellite. As this posts, this storm is about to make landfall in China as about a category 3 storm, after having skirted over several smaller islands and the northern tip of Taiwan.

Last week, this storm underwent one of the most rapid intensifications on record, going from a tropical storm to a super-typhoon in under 16 hours. Warm waters in the Western Pacific are sustaining the storm.

Storms like Maria forming in the Pacific Ocean can drive winds that push equatorial waters to the East. This storm can therefore be on symptom of a developing El Niño event, which may occur later this year based on current forecasts.

Last year, a major hurricane named Maria also struck Puerto Rico. In the Atlantic Basin, because of the devastation of that storm, that name has been retired. However, that name is also being used in the Pacific Basin, so we have 2 major hurricanes in two years both carrying the name Maria.

-JBB

Image credit: NASA/Aqua/MODIS

https://earthobservatory.nasa.gov/images/92409?src=eoa-iotd

More:

https://twitter.com/MichaelRLowry/status/1015040789091618816

https://weather.com/en-CA/canada/news/news/2018-07-09-western-pacific-typhoon-maria

A glimpse inside a super typhoon.

This is an internal profile of super-typhoon Uusagi, which struck Taiwan and the Philippines in 2013 (see http://tinyurl.com/mgdebue). As it approached Taiwan, a satellite borne radar system took this image of a meteorological phenomenon called hot towers in the outer eyewall of the typhoon along with the rain that was belting down in varied parts of the weather system. Hot towers are rapidly rising cumulonimbus anvil clouds that carry the moisture rapidly upwards up to an altitude of 15km. They can rise so high as to punch into the stratosphere depositing ice crystals. They are named after the immense amount of latent heat held by their moisture that is released as they condensate into rain.

The appearance of hot towers indicate a strengthening storm, and reveal the heat engine of rapidly rising moist air driving the typhoon. Shortly after this image was taken, Usagi briefly strengthened to category 5, the highest on the scale Both the eyewall and rainfall pattern are very symmetrical for a cyclone, and indicate an energy efficient system. Such annular eyewalls tend to indicate longer lived cyclones, as they do not dissipate their energy as much as turbulence.

Loz

Image credit: Owen Kelly/ NASA

http://earthobservatory.nasa.gov/blogs/earthmatters/2013/09/23/a-view-inside-super-typhoon-usagi/?src=fb

http://earthobservatory.nasa.gov/blogs/earthmatters/2012/09/12/discovering-hot-towers/

http://earthobservatory.nasa.gov/Features/Simpson/simpson3.php

Super Typhoon Usagi This image was taken by the MODIS instrument on NASA’s Aqua Satellite on September 19th, 2013. At the time, the storm seen in this image, Super Typhoon Usagi was the equivalent of a category 4 storm with 140 mph/225 kph winds. After this shot was taken it moved over very warm waters (29 - 30°C) and strengthened into the first category 5 storm of the year, with wind speeds up to 162 mph/260 kph. -JBB Image credit: NASA Press report http://www.cnn.com/2013/09/20/world/asia/typhoon-usagi/?hpt=wo_c2 WUnderground update: http://www.wunderground.com/blog/JeffMasters/article.html?entrynum=2527 Press report: http://www.foxnews.com/world/2013/09/20/super-typhoon-usagi-on-path-destruction/

What are cyclones?

A cyclone is a huge system of rotating wind around a large scale low pressure area called “eye”.

The rotation of wind is anti-clockwise in the Northern Hemisphere and clockwise in the South. This is due to Coriolis force which acts on a moving body (Wind) in a rotating reference frame (Earth).

Tropical Cyclones are known by different names in different areas: • Hurricanes in the North Atlantic & Eastern Pacific • Typhoons in Western Pacific

Tropical Cyclones arise over ocean in the tropical latitudes (5°N - 15°N) where Coriolis force is substantial enough to stabilize its low pressure eye.

There are two factors that fuel its growth:

If Tropospheric Vertical Shear (change of wind velocity with height) is low, the storm builds into a cyclone within two to three days. Otherwise, frequently changing speed and direction of wind in upper atmosphere would halt the progress of storm in the upward direction.

When formed, a cyclone is roughly 600km across and 15km high. The winds in it can speed over 100kmph.

The eye of a cyclone is the region of lowest pressure and highest temperature (as compared to surrounding region). It experiences relatively calm wind and fair weather. It is usually about 50km across.

After the cyclone is formed, it is steered by Trade Winds (Global Winds that blow predominantly from east to west in the Northern Hemisphere) which is responsible for Hurricane Landfalls in North America.

After reaching the land, the break in chain of evaporation and condensation diminishes the energy of the cyclone. Hence, it dies within few days after landfall.

The fancy names of Tropical Cyclones are basically to facilitate easy communication. A list of 21 names (beginning with alphabets excluding Q, U, X, Y and Z) is prepared for each year. The first tropical storm in that year is given the name with A; the second storm is given the name with B and so on.

-TT

(Photo Source: NASA http://img.mit.edu/newsoffice/images/article_images/original/20120113095712-1.JPG

Article References: 1. NOAA - http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqHED.html 2. http://library.thinkquest.org/05aug/00181/how%20a%20hurricane%20forms.htm 3. Earth Science - http://ows.ettruck.com/items/show/21

For further study: 1. http://www.windows2universe.org/earth/Atmosphere/hurricane/formation.html 2. http://www.windows2universe.org/earth/Atmosphere/hurricane/movement.html 3. http://spaceplace.nasa.gov/hurricanes/)

Notable Tropical Cyclones

Here’s a look back at some of the worst cyclones to hit the the eastern hemisphere area since the year 2001. 

One particular storm, Hurricane/Typhoon Ioke was the strongest ever recorded cyclone in the Central Pacific Basin. It formed southeast of Hawaii in late August, 2006 and strengthened to a hurricane on August 21. It crossed the International Date Line, which resulted in a change of its designation from a hurricane to a typhoon. It attained the maximum category 5 strength three times, with wind speeds over 260 km/h (160 mph). The storm lasted 17 days, with a minimum pressure of 915 mbar, the lowest estimated pressure for a cyclone in the Central Pacific Basin. Ioke maintained winds of at least category 4 status (211 km/h) for 198 consecutive hours, the longest ever observed for any tropical cyclone on Earth. The storm passed near Johnston Atoll and Wake Island, which sustained some damage, but it managed to avoid permanently populated areas.

This graphic, as well as one for the other half of the world appears in "The Global Climate 2001-2010: A Decade of Climate Extremes" summary report from the World Meteorological Organization.

-Amy

References:

http://library.wmo.int/pmb_ged/wmo_1119_en.pdf

http://www.australiasevereweather.com/cyclones/2007/summ0608.htm

http://www.prh.noaa.gov/cphc/summaries/2006.php

Image Credit World Meteorological Organization

Typhoon Soulik targeting Taiwan, China

This image was taken on July 10, 2013, by the MODIS instrument on NASA’s Aqua satellite. At the time of this image, Typhoon Soulik was a category 4 storm, with an exceptionally well-defined eye-wall. At the time of this image it was the strongest storm of the season in the Western Pacific, and was en route to landfall on Taiwan.

-JBB

Image credit, NASA image, found at: http://jramosgarcia.wordpress.com/2013/07/10/soulik-noroeste-del-pacifico/

Tracking map and history from Weather Underground: http://www.wunderground.com/tropical/tracking/wp201307.html

Nepartak

Second Largest Volcanic Eruption of the 20th Century

This week is the 25th anniversary of both the devastating Mount Pinatubo eruption, and of Typhoon Yunya hitting the Philippines. These two natural catastrophes struck the densely populated island of Luzon on June 15, 1991.

Prior to 1991, Pinatubo was a heavily forested lava dome that had been dormant for 500 years. Little was known about the stratovolcano. When it begin to show signs of life in March of 1991, first with earthquakes rumbling beneath it and then by relatively small ash explosions, scientists had very little information to predict what might happen next. Researchers quickly moved to install seismic monitors and survey the mountain. To their dismay, they discovered Pinatubo had a history of very large eruptions.

The mountain and the surrounding area were home to hundreds of thousands of people. An additional 15,000, US military personnel and their families, lived at Clark Air Force base. As seismicity, deformation of the mountain, and emission of small plumes increased, the people living on the mountain and those closest to it were evacuated in stages. Then on June 7, the first magma began to reach the surface. By June 9, over 50,000 locals had been ordered to leave. On June 10, all but 1,500 military personnel and the scientists monitoring Pinatubo were ordered to evacuate Clark.

At 8:51am on June 12 (Independence Day in the Philippines), Pinatubo erupted explosively, sending a column of ash and steam 19 kilometers (11 miles) into the air. It subsided after 40 minutes, but the earthquakes didn’t; the mountain wasn’t done. All residents within 20 kilometers of the mountain were told to evacuate. Another 600 at Clark were told to leave as well.

The morning of June 15, Typhoon Yunya struck Luzon even as the mountain continued to erupt with smaller explosions. Fortunately the storm was already dissipating into a tropical storm. Even so, it brought heavy rains and circular winds. Then, around 1:42pm local time, Pinatubo exploded with the second largest eruption in the 20th century. The explosion ejected 5 cubic kilometers (1 cubic mile) of material. Much of the mountain summit was removed by explosions or collapse, leaving a caldera 2.5 kilometers (1.6 miles) across. The ash cloud rose 35 kilometers (22 miles) into the air. At lower altitudes, ash that would’ve blown out to sea was caught in Yunya’s circulating winds, and then brought back down on Luzon by the rain. The heavy, wet ash came down like mud and accumulated on rooftops, collapsing many of them. Pumice, including some the size of apricots, began to fall on Clark and the nearby city of Angeles, in some cases causing injuries. Lahars and debris came down the mountain and filled some valleys 200 meters (660 feet) thick. Many people fled and more evacuations were ordered; all together, the eruption dislocated about 250,000 people.

Pinatubo continued to erupt for several days, but the worst was over and some people began to return to their homes. Ash continued to erupt and was reported to be 15-30 centimeters thick at Clark and some of the surrounding towns and cities. So much ash was expelled throughout the eruption that it would eventually cause a short-term global cooling of 0.5-degrees Celsius.

The eruption finally ended in September. Over 105,000 homes were damaged or destroyed, and the thick layer of ash over once fertile agricultural lands caused long-term hardship. There was so much ash that new lahars formed during monsoon seasons for several years after, in one case killing 60 people. In June of 1992, about 70,000 were still living in evacuation centers and resettlement areas. Clark was permanently abandoned.

Amazingly, the death toll was only about 725. The evacuations are believed to have saved the lives of 20,000 people.

Pinatubo begin to erupt again in July of 1992 from a caldera lake that now exists where the mountain summit used to be. It erupted again in February of 1993. Fortunately the eruptions were relatively small. The volcano finally went quiet, and, based on past history, probably won’t erupt again for hundreds of years.

Photo Credit: Richard P. Hoblitt, U.S. Geological Survey, http://bit.ly/1S0AQsa R.S. Culbreth U.S. Air Force, https://www.flickr.com/photos/kyngpao/8874135744/ USGS / Cascade Volcano Observatory, http://bit.ly/1rj2sDh E.J. Wolfe, http://bit.ly/1ZHrxU1 References: http://pubs.usgs.gov/fs/1997/fs113-97/ http://gsabulletin.gsapubs.org/content/117/1-2/195.full http://volcano.si.edu/volcano.cfm?vn=273083 http://bit.ly/1tuS3Go http://bit.ly/1SkSzjg Previous Earth Story Posts: http://bit.ly/1UnCM3S http://bit.ly/1ufd6VQ

The Uncertain Future of Tropical Cyclones

The last few years have seen an alarming number of extremely strong tropical cyclones in various ocean basins across the world. In November 2013, Typhoon Haiyan became the strongest landfalling tropical cyclone in recorded history when it crashed into the Phillipines with 305 km/h (190 mph) sustained (1-minute average) winds. Just this past October, Hurricane Patricia in the East Pacific became one of the strongest tropical cyclones ever recorded when it achieved a minimum surface pressure of 872 mb with sustained winds of 345 km/h (215 mph). This made it the second-strongest reliably measured tropical cyclone in world history by pressure and the strongest by wind speed. And most recently, Tropical Cyclone Winston devastated the South Pacific island nation of Fiji when it passed through the archipelago with sustained winds of nearly 300 km/h (185 mph), making it the Southern Hemisphere’s strongest storm on record and the second-strongest landfalling storm globally.

Such events have led many people to invoke climate change as an explanation for this rash of severe tropical cyclones. However, making such a connection is not quite as simple as it seems. Tropical cyclones are, at their most basic, heat engines. The greater the heat content of the oceans beneath them, the greater intensity they have the potential to achieve. Thus, in the absence of any other factors, warmer oceans produce more intense tropical cyclones. However, climate change also modifies other factors affecting tropical cyclone development, such as wind shear and atmospheric instability. Each of these factors merits an entire post in their own right; for the sake of brevity, however, their effects will be described just superficially here.

Wind shear is a measure of how the wind speed and direction changes through the depth of the atmosphere. In the tropics, wind shear is typically low, and lower wind shear is necessary for the development of tropical cyclones. Due to the way in which climate change is expected to rearrange global circulation patterns, however, wind shear may actually increase in some ocean basins (such as the Atlantic), and would thus reduce the number and intensity of tropical cyclones.

Atmospheric instability describes how rapidly temperatures cool with height through the atmosphere. Warmer surface temperatures are one way to generate greater instability, but climate change will actually result in more warming of the middle and upper portions of the tropical atmosphere (the upper troposphere). Instability in the tropics is therefore likely to slightly decrease, if anything, in a globally warmed world.

Overall, the consensus among tropical cyclone researchers is that the interplay between these factors will result in fewer but more intense tropical cyclones globally. That is, when wind shear and instability are favorable for cyclone development, the warmer oceans of the future will be capable of generating more powerful storms. While favorable wind shear and instability were certainly present for all of the record-setting tropical cyclones of the past few years, so too were record-warm sea surface temperatures. While no one event is ever “caused” by climate change, what we can say is that recent intense storms like Haiyan, Patricia, and Winston were very likely enhanced by anthropogenic climate change. When this threat is coupled with sea level rise, it looks like a very risky future indeed for many tropical nations.

--BRC

Image credit: http://go.nasa.gov/1VU6Fam

References: http://1.usa.gov/1te1Fy9 http://bit.ly/1p4VzVO

In late August, Tropical Storm Kilo formed in the central Pacific. The storm didn’t hit land or cause much damage, but scientifically it was a very interesting storm. It lasted nearly 3 weeks, churning in the middle of the ocean, intensified from a tropical storm to a hurricane, and crossed the International Date Line so that it went from being a hurricane to a typhoon. Because of its long life, NASA satellites made multiple passes over the storm and were able to monitor its evolution, a story told in this video.

This satellite water vapor loop shows typhoon Atsani  at the center of the frame and Typhoon Goni in the west, on its way towards the Japanese island of Kyushu.  Kyushu is already worrying about one major threat - the awakening Sakurijima Volcano, so the impact of a typhoon is just another major issue. http://www.accuweather.com/en/hurricane/west-pacific

Really neat dashcam weather video. This took place in Taiwan, right after the impact of typhoon Soudelor. A driver makes a quick turn onto a road and then his car is immediately consumed by a tornado spawned by the typhoon. I’m trying to figure out if the person in the road after it passes was originally driving the car and ditched out of it, I think he was. 

Four in a row

The northern half of the Pacific Ocean was looking busy a week ago, with two fully fledged typhoons, one tropical storm and another brewing low pressure feature. From left to right they comprise Tropical Storm Linfa in the South China Sea, Typhoon Chan Hom in the East China Sea, Typhoon Nanga near Guam, and a maturing storm near Hawaii that isn't expected to develop into anything significant.

Loz

Image credit: JMA MTSAT-2/NOAA