Land Degradation Due to Agriculture:

Part 3 Impacts of Deforestationand Soil ErosionFall 2012 , Lecture 7

Earth ObservatoryImage

• On March 19, 2012, MODIS, on NASA’s Terra satellite, captured this natural-color image of a storm sweeping across Iran, Afghanistan, and Pakistan

• Some source points are visible in southern Afghanistan, and the dust blew in southeast-northeast arcs

• Most of the dust plumes in this storm were thick enough to completely obscure the land and water surfaces below

2

Soil Loss• Deforestation often leads to soil erosion• Agricultural use of land can also produce soil

erosion Modern methods used in advanced countries have

greatly cut these losses In developing countries, agricultural soil loss is still a

major problem3

On-site Impacts of Soil Erosion• Reduction in soil quality resulting from

Loss of the nutrient-rich upper layers of the soil Reduced water-holding capacity of many eroded soils

• Increased use of artificial fertilizers can mitigate the first problem in developed countries

• Not an option in most developing countries

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Time-Scale of Problems• On-site impacts of soil erosion are a present-day

problem for many of the developing nations• For developed nations, on-site impacts will be a

problem only in the long term future because they are outside the relatively short time horizon within which their policy makers work

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Off-site Impacts of Soil Erosion• Water erosion’s main

off-site effect is the movement of sediment and agricultural pollutants into watercourses

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• China's Yangtze River at the Three Gorges, in Hubei province. Note the sediment-rich water

Watercourse Sedimentation

• Sediment in watercourses can lead to the silting-up of dams, disruption of the ecosystems of lakes, and contamination of drinking water

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• Satellite view of the delta of the Yangtze River as it discharges into the East China Sea. The sediment plume is clearly visible. (Image: NOAA)

Down-stream Flooding• Increased downstream flooding may also

occur due to the reduced capacity of eroded soil to absorb water, and to the reduced capacity of streams and lakes to hold water

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Time-Scale of Off-Site Problems• Short-term effects of erosion's off-site effects can be

a notable problem for developed nations• Policy change in developed countries may be driven

by off-site impacts• For less developed nations, there may be less

incentive for short-term policy change

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Examples of Soil Erosion • We will examine soil loss in several areas

Indonesia Madagascar Haiti

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Kalimantan, Borneo, Indonesia • In less than 25 years, three-

quarters of Kalimantan, which occupies a large part of the Island of Borneo in Indonesia, half of the thick forests have been cut by loggers for agricultural land, including oil palm plantations

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Agricultural Land Clearing• Kalimantan locals have

long burned forestland to create plots for farming

• Formerly small, controlled fires were used

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“A” is Borneo, in relation to SE Asia

Drying the Land• As deforestation has progressed, the island has

become drier• The small fires have changed to

conflagrations • The cause is burning peat

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Loss of Swamp Land• Peat has formed over thousands of years from decomposed

trees, grass and scrub • It contains huge quantities of carbon dioxide• Formerly, that was safely sequestered in the ground• Deforestation has caused drying, and the peat is disintegrating• Once-soggy swamps are shorn of trees and drained by canals• When peat burns, carbon dioxide gushes into the atmosphere

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Indonesian Photo Gallery• Washington Post Photo Gallery – Indonesia• The link is from a story “A climate threat,

rising from the soil”, by Andrew Higgins, which appeared in the Washington Post on November 19, 2009

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CO2 from Peat Burning• Wetlands International, a Dutch research and lobbying group, estimated

Indonesia's peatlands released roughly 1.9 billion metric tons of carbon dioxide in 2006

• This was equal to the combined emissions that year of Germany, Britain and Canada, and more than U.S. emissions from road and air travel.

• In 1997, particularly bad fires raged across Kalimantan and, according to a study led by a British scientist, the amount was up to four times as high -- more than the total emissions by the United States in that period

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Economics versus the Environment• Logging and palm oil companies deploy

formidable resources across Kalimantan• These are both economic, and physical forces,

used against environmental activists trying to protect the fragile peat

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Palm Oil Operations• At the PT Globalindo Agung Lestari, an oil palm

estate, a wooden barrier separated a dozen or so out-of-town environmental activists with a bullhorn

• On the other side, company security guards, local police officers and Indonesian soldiers, armed with automatic weapons, stood ready

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Supporting the Company• Villagers were angry at the plantation, but had to stay

away• They couldn’t afford to lose their jobs tending oil palm• The pay is about $3 a day and the work is backbreaking• Budi, a 21 year old worker, said "when you don't have

anything, you have to support the company"

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Ethics vs. Economics

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This video, from Time movies, shows the ethical problems faced by indigenous peoples, when choosing to exploit the environment or be unemployed

Erosion in Action• Video clip shows

erosive rainfall in a region of steep topography in Indonesia

• The effect of vegetation removal is evident

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Kuala Cenaku, Riau Province,

Indonesia

• Riau is a province of Indonesia, located in the center and eastern coast of Sumatra along the Strait of Malacca

• Extensive logging has led to a massive decline in forest cover from 78% in 1982 to only 33% in 2005

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WWF Information• Riau Province is the home of two of the world’s largest pulp mills,

produces more than two thirds of Indonesia’s pulp, and is covered with more timber plantations and more oil palm concessions than any other province in Indonesia

• Between 1988 and 2005, half of Riau’s forests disappeared at an average rate of 170,000 hectares per year or 460 hectares per day

• The loss of some of the most diverse forests on earth is accelerating rapidly - the annual rate of forest cover loss was 2.2% in 2002, 4.2% in 2004 and 6.8% in 2005

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Peat Depth• According to Indonesian law, it is illegal to

clear forest where peat exceeds 3 meters in depth

• The law is largely ignored, with disastrous consequences

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Greasy Palms: The Impact of

Indonesia’s Palm Oil

Plantations• Video from

the Paradigm Shift Project

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Air Pollution• A final problem caused by fires in the thick peat

deposits is severe air pollution• The haze can travel hundreds of miles in SE Asia• The following video shows the effects in Malaysia• The video also some of the products palm oil is used

for

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Malaysian Haze Video

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Madagascar• Fourth largest island in the world• Madagascar split from India around 88 million

years ago, allowing plants and animals on the island to evolve in relative isolation

• Isolated areas often see less evolution than other regions

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Restricted Evolution• In Madagascar, there are no woodpeckers or

ungulates (hooved animals) present• Instead, animals like lemurs dominate rare

ecosystems, present no where else on earth• More than 200,000 known species are found on

Madagascar, and about 150,000 exist nowhere else

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Madagascar History• Beginning in the early 19th century, most of the island was

united and ruled as the Kingdom of Madagascar by a series of Merina nobles (Merina is the largest cultural sub-group)

• Collapse of the monarchy occurred in 1896 when the island was conquered and absorbed into the French colonial empire, from which the island gained independence in 1960

• The autonomous state of Madagascar has since undergone four major constitutional periods, termed Republics

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Coup d'état• Since 1992 the nation has officially been governed as a

constitutional democracy from its capital at Antananarivo• However, in a popular uprising in 2009 the last elected

president Marc Ravalomanana was made to resign and presidential power was transferred in March 2009 to Andry Rajoelina in a move widely viewed by the international community as a coup d'état

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Patricia Wright• Before Rajoelina came to power, the state of

Madagascar's ecological health was actually improving, according to Patricia Wright, professor of anthropology at the State University of New York at Stony Brook, executive director for the Institute for the Conservation of Tropical Environments, and a recipient of a MacArthur Foundation "genius award"

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Wright’s Opinion• “It's one of the success stories in all of the conservation

world. Because of big inputs from conservation agencies — U.S. AID [Agency for International Development], the European Union — the infrastructure of the country improved. The protected areas were being protected. Everything looked really optimistic for keeping the island's forests in place.”

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Effects of the Coup d'état• The problem with the coup d'état, according to Wright,

“Everyone assumes they can literally take anything they want. So we have major rosewood being extracted from the beautiful forests in the north. We have a certain amount of lawlessness that's going on, also in the north. Inside protected areas, the National Park Service [rangers] abandoned their posts because they were afraid. They've since returned, but it's been a very difficult year for protecting wildlife.

34

Tavy• “Tavy” is a Malagasy word for the slash and burn agriculture practiced

in Madagascar• An acre or two of forest is cut, burned, and then planted with rice• After a year or two of production the field is left fallow for 4-6 years,

then the process is repeated• After 2-3 such cycles the soil is exhausted of nutrients and the land is

likely colonized by scrub vegetation or alien grasses• On slopes, the new vegetation is often insufficient to anchor soils,

making erosion and landslides a problem

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Economic Necessity• Madagascar is among the world's poorest countries• As such, people's day to day survival is dependent upon

natural resource use• Where day-to-day subsistence is a question, people show little

concern for the long-term consequences of their actions• As long as there is more forest land freely available for

clearing, you might as well use the land before a neighbor does.

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Erosion in Madagascar

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Seen from the air

Erosion in Madagascar

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• Betsiboka River, Madagascar, running like liquid chocolate, January 2012

• Astronauts have remarked that it looks as if Madagascar is bleeding to death, with its rivers running blood red and staining the surrounding Indian Ocean

Image from Space

• Nearly a century of extensive logging of Madagascar’s rainforests and coastal mangroves has resulted in nearly complete clearing of the land and fantastic rates of erosion

• After every heavy rain, the bright red soils are washed from the hillsides into the streams and rivers to the coast

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This image of the Betsiboka Estuary on the northwest coast of Madagascar reveals the mouth of the country’s largest river and one of the world’s fast-changing coastlines

NASA Description• Astronauts describe their view of Madagascar as 'bleeding into

the ocean' • One impact of the extensive 20th century erosion is the filling

and clogging of coastal waterways with sediment - a process that is well illustrated in the Betsiboka estuary

• In fact, ocean-going ships were once able to travel up the Betsiboka estuary, but must now berth at the coast

40

Malagasy Agriculture• Agriculture is the mainstay of the Malagasy economy, using

80% of the labor force • Deforestation, unsustainable farming methods, low

productivity and insecure land tenure are all fuelling diminishing soil yields and threatening the island's food security, putting the agriculture section at risk

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Agroecological Techniques• The Agence française de développement (AFD) is developing,

the use of agroecological techniques with Malagasy farmers• This approach involves protecting the soil with a green cover

crop, as a way of avoiding plowing, and restricting the use of fertilizers

• Soil fertility is restored, watershed erosion is reduced and as are CO2 emissions

• The video on the next slide explains the use of agroecology

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Agroecology in Madagascar

43

Haiti• Haiti occupies the western

third of the island of Hispaniola, which is situated in the Caribbean between Cuba and Puerto Rico

• The Dominican Republic occupies the remainder of the island

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• The Atlantic Ocean borders Haiti’s northern shores, while the Caribbean Sea is to the west and south

Haitian Topography• Haiti occupies the mountainous portion

of the island of Hispaniola• Five mountain ranges dominate Haiti’s

landscape and divide the country into three regions northern, central, and ⎯southern

• Slopes of more than a 20 percent grade cover nearly two-thirds of the country

• Plains constitute only about 20 percent of Haiti’s land, making cultivation difficult

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Haitian Deforestation• Haiti faces a severe deforestation problem• In 1923, forests covered nearly 60 percent of the

country; today they cover less than 2 percent• Wood and charcoal are the primary fuel source

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Beginnings of Deforestation• At the onset of colonialism, Haiti began to suffer deforestation• Around 1730, coffee was introduced, producing a monoculture

agriculture• Within 50 years upland forest clearing resulted in 25% of the

land being under coffee• Other crops included indigo, tobacco, and sugarcane• Clean cultivation between row crops exhausted nutrients and

lead to erosion

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Nineteenth Century• Throughout much of the 19th century, the

government was forced to export timber to repay a large debt to France

• Peasants were restricted to hillside farms, where often steep slopes lead to severe erosion

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Poverty• Lack of economic capital make farming difficult• Average per capita income is less than one-seventh

of the average for Latin America and the Caribbean• With inheritance, land is subdivided, and plots grow

increasing smaller• One estimate claims the average peasant has less the

one-quarter of a hectare49

Leased Land• Many families lease or sharecrop additional

land• Farmers on leased or share-cropped land have

little incentive to take care of the land• In addition, most agricultural work is by hand,

with no mechanical equipment

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Lack of Government Aid• The government has been controlled by a

string of dictators for many years• They are much more intent on enriching

themselves, not using the few resources they have to improve conditions

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Effects of Deforestation• Deforestation has a number of effects

Soil erosion• Soil erosion has decreased agricultural yields• Soil erosion into the ocean also blankets coral reefs with sediment, killing

the reefs

Floods due to disruption of the natural hydrologic cycle Landslides

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Flooding• When vegetative cover is removed from the

land, the rate of infiltration decreases dramatically

• Since water has to go somewhere, if it can’t infiltrate, it runs off

• Rapid runoff leads to flooding

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Haiti’s Unnatural Floods

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Landslides• Landslides have also been a frequent cause of

death in Haiti• For example, there was a landslide in late

March of 2012 in which six people in Port-au-Prince were killed by a landslide

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Tropical Storm Hanna, 2008• As Hurricane Hanna approached Haiti in September

2008, Dave Petley (Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the United Kingdom) blogged on an American Geophysical Union site that 136 people have been killed in flash floods and landslides as a result of Hanna, but time might reveal more casualties

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Haiti-Dominican Republic Border• The river in the photo is the

border between Haiti (left) and the Dominican Republic (right)

• The lack of vegetation in Haiti has made landsliding a tremendous problem

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Aftereffects of Gustav/Hanna• On August 26, 2008 Hurricane Gustav brought strong

winds and heavy flooding to Haiti• On 1 September 2008, only days after Gustav hit

Haiti, Tropical Storm Hanna surprised the country, worsening the effects of Gustav and leaving more people affected, especially in the city of Gonaives

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Post Storm Damage Estimates• According to Haitian government statistics:

A total of 793 people lost their lives 310 were declared missing 548 were injured Damage to homes and infrastructure affected 165,337 families

• It is estimated that 22,702 families’ homes were completely destroyed • Another 84,625 families’ homes were damaged

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Aftereffects of Haitian Storms, 2008• This is a series of

still photos showing the aftereffects of the 2008 Haitian storms

• Note especially the extent of the flooding

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Video Interview• The following video interview by Amy

Goodman, the host of Democracy Now!, an independent global news program broadcast daily on radio, television and the Internet, with Dr. Paul Farmer

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Paul Farmer, M.D.• Paul Farmer is an American anthropologist and physician• Named chairman of Harvard Medical School's Department of

Global Health and Social Medicine in May 2009• In December, 2010, Harvard University's President, Drew

Gilpin Faust, and the President and Fellows of Harvard College, named him a Kolokotrones University Professor of Harvard University, the highest honor that the University can bestow on one of its faculty members

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Partners in Health• This video conveys the magnitude of the problems that Haiti

faces, much of which has been caused by deforestation• Dr. Farmer co-founded Partners In Health, which began in

Cange in the Central Plateau of Haiti and has developed into a worldwide health organization

• His extensive experience in Haiti and other third world countries give him a perspective most commentators do not have

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Farmer Interview

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Haitian Earthquake• On January 12, 2010 Haiti suffered a magnitude 7.0

earthquake,  which caused the death of more than 200,000 people, the injury of about 300,000 people, and left about two million people homeless

• A year and a half prior to the earthquake, Haiti was subjected to another severe disaster, flooding induced by two hurricanes and two tropical storms (Fay, Gustav, Hanna and Ike)

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Hurricane-Earthquake Connection?• Both natural disasters results in death and

destruction, but because their origins are very different, they are generally considered to be unrelated phenomena

• A pr by Shimon Wdowinski et al. suggested there may be a connection

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Earthquake Location• The earthquake was thought

to have occurred along the Enriquillo-Plantain Garden Fault, part of the fault system that separates the North American plate to the north from the Caribbean plate

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Previous Tectonics• In 1770, there had been a large earthquake to

the west of Port-au-Prince• GPS measurements suggest that the underlying

tectonics are a left lateral shear at 8 mm per year and shortening (convergence) at about 5 mm per year

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Strike and Dip

The strike-dip symbol, used on geologic maps, is shown - the long direction points in the horizontal direction, and the shorter side

shows dip direction

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Strike-slip Direction

• Strike-slip faults are further described as "right-lateral" or "left-lateral" depending if the block opposite the viewer moved to the right or left, respectively

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Left-Lateral Strike Slip• Block is displaced to the

left, looking across the fault

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Strike Slip Faults - Left Lateral

Near Lillooet, British Columbia

Westward Movement• So the previous work indicated that the area

north of the fault was moving west relative to the area south of the fault

• The earthquake showed westward movement on the Enriquillo fault, but there was no evidence of surface rupture on that fault

73

Discovery of a New Fault• Post earthquake investigations suggest shortening as well as

strike slip movement• The data suggest a different fault, not the Enriquillo fault, was

responsible for the earthquake• This new fault, which is orientated sub-parallel to the

Enriquillo Fault, is now known as the Leogane Fault, with a combination of strike slip and dip slip movement

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Dip-slip Faults

• Dip direction is always perpendicular to the strike line

• Combination of dip and strike slip produces oblique-slip

Fault Models• From remote sensing data it was evident there was no surface

rupture• There was evidence of coastal uplift• Measurement of the uplift suggested movement of about 64

cm over a distance of 50 km of coast• Two fault models have been proposed to explain this, one with

movement along two faults, the other with movement along three faults

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Movement on a Blind Fault• Both models suggest that most slip was on

south dipping blind fault.• A blind fault is one which does not reach the

surface• The presence of blind faults is often unknown

until an earthquake reveals their presence

77

Haitian Scientific Effort• Jean Altidor, from the Haiti Bureau of Mines and

Energy, working with the USGS and the Canadian natural resource bureau, deployed seismometers in March 2010 to measure aftershocks

• Worked with various other groups to undertake geological and geodetic measurements

78

Earthquake Amplification• Found that downtown Port-au-Prince is

underlain by soft sediments• Soft sediment behaves like a bowl of jello

during an earthquake and will amplify shaking, causing much greater destruction

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Sediment Unloading• Wdowinski et al. suggest that the hurricanes trigger surface

unloading due to rapid erosion, which then triggers the earthquake

• Unloading may decrease pressure perpendicular to the ground’s surface

• In the case of the earthquake, movement on the fault was atypical (dip slip)

80

Leogane River and

Delta

81

Google Earth Image

• “Google Earth image of Haiti taken November 8, 2010, showing the capital of Port-Au-Prince and the mountainous region to its west where the epicenter of the 2010 earthquake was. Note the brown color of the mountains, where all the vegetation has been stripped off, leaving bare slopes subject to extreme erosion. Heavy rains in recent years have washed huge amounts of sediment into the Leogane Delta to the north.”

82(From figure caption on Dr. Jeff Masters blog)

Leogane Delta• Zoom-in view of the Leogane Delta region of previous figure, showing the large expansion in the Delta's area between 2002 and 2010. High amounts of sediments have been eroded from Haiti's deforested mountains and deposited in the Delta. Recent expansion of the river channel due to runoff from Hurricane Tomas' rains is apparent in the 2010 image. Image credit: Google Earth, Digital Globe, GeoEye.

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(From figure caption on Dr. Jeff Masters blog)

Rapid Erosion as Earthquake Trigger• Hurricane induced rapid erosion in the mountains

would release downward pressure, allowing vertical movement

• Previous movements were estimated at 5 mm per year of convergence, which would produce vertical uplift

• Reducing load might act as a trigger, allowing movement to initiate

84

Sediment Deposition in Delta•  The calculated sediment deposition in the

delta of the river draining the mountains gives an erosion rate of 6 mm per year

• This is much higher than expected, and is due to deforestation

85

Digitial Elevation Model• A (DEM) was used to calculate stress change at the earthquake

focus due to sediment unloading• Wdowinski et al. modeled resultant stress change on the fault• The model shows that unloading promotes fault movement on

a south dipping fault and that the magnitude of change is at least hypothetically able to trigger the earthquake

86

Delay Between Hurricane and Earthquake• Why was there a delay between the hurricane and the

earthquake? • Possibly the increased soil moisture help to keep normal

stress high, due to the increased mass of the water in the soil• Once the soil dries out, mass is reduced, causing a reduction

in normal stress• Fault movement may have resulted

87

Hypothesis, not Theory• This is a very interesting speculation• However, it is a hypothesis• The paper was presented at a meeting of the

American Geophysical Union in the Fall of 2010, but has yet to appear in the scientific literature, possibly due to peer review comments

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