Catastrophic Events Think – What is a catastrophic event? Share – with a partner/class A catastrophic event --- involves or causes a sudden terrible disaster Examples: hurricanes, tornadoes, floods (weather events) The impacts of these events on ecosystems can result in changes to landforms as well as changes to populations and species.

Hurricanes October 23 picture from the International Space Station of Hurricane Patricia http://video.nationalgeographic.com/video/101-videos/hurricanes-101 http://www.history.com/shows/history-originals/videos/science-of-a-hurricane

Hurricanes On average, ten tropical storms develop over the Atlantic Ocean, the Caribbean Sea, or the Gulf of Mexico each year. About six of these develop into hurricanes Many of these storms remain over the ocean.

Hurricanes Hurricanes start out as tropical depressions, then develop into tropical storms (tropical cyclones). When the winds reach a constant speed of 74 mph or more, it is upgraded to a hurricane. Hurricane winds blow in a spiral around a calm center called an eye. The eye can be up to 30 miles wide and the storm can be 400 miles in diameter.

Hurricanes A hurricane can have torrential rains, high winds, and a storm surge as it approaches land. Most deaths from hurricanes are due to flooding. Winds can drive ocean water up the mouth of rivers. When hurricanes move onshore, they impact the ecosystem in a variety of ways, including a storm surge of seawater along the coast. As it moves across land, intense wind damage and excess flooding events occur all along the path of the storm. Frequently, tornadoes form within hurricanes.

Hurricanes Flooding can trigger mudslides or landslides. Tornadoes can be spawned by hurricanes. Economic costs and habitat loss is common. Hurricanes may have several major negative impacts on the structure and function of ecosystems, such as uprooting trees, destroying animal life, and destroying habitats as well as completely stripping vegetation.

After Katrina Before Katrina

Hurricanes affect the Gulf Coast Prairies and Marshes Ecoregion of Texas

Hurricane Ike, 2008 Photos and information from USGS http://coastal.er.usgs.gov/hurricanes/ike/photo-comparisons/bolivar.html

Location 1: Oblique aerial photography of Bolivar Peninsula, TX, on September 9, 2008. Yellow arrows mark features that appear in each image.

Location 1 September 15, 2008, two days after landfall of Hurricane Ike.

Location 1 In addition to the loss of houses, the evidence of inundation here includes eroded dune face and sand deposited well inland of the shoreline.

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Oblique aerial photography of Galveston, TX, on September 9, 2008 (top) and September 15, 2008, two days after landfall of Hurricane Ike (bottom). Yellow arrows mark features that appear in each image. Hurricane-induced waves and surge destroyed a small walkway. Coastal-change impacts include beach and dune erosion, and the removal of considerable dune vegetation. This location is on the right-hand side of the hurricane track and likely experienced the strongest winds, highest surge, and waves.

When Hurricane Katrina smacked the Gulf Coast in August 2005, the protection from powerful storm surges provided by coastal wetlands and barrier islands had gradually been whittled away. Since the 1930s, Louisiana had lost 1.2 million acres of coastal wetlands. More than two dozen dams and thousands of miles of levees on the Mississippi River had trapped sediment that otherwise would have replenished them.  The disintegration of the Chandeleur Islands, Louisiana

Writing Catastrophic events, like hurricanes, are natural occurrences that generally have a negative effect on people and/or the environment. — Is there any time a hurricane could have a beneficial effect of the environment? — How would the ability to predict a hurricane’s impact (not just landfall) ahead of time be beneficial to people and the environment?