Earth Science

How are Hurricanes Classified?

Hurricane Fran

Hurricanes are classified on the Saffir/Simpson Hurricane Damage-Potential scale. This scale assigns a number from 1 to 5 based on the potential disaster the winds and storm surge of the hurricane may cause.  The scale was developed by Herbert Saffir and Robert Simpson in 1971. It’s primarily used today for allowing disaster agencies to prepare for imminent storms and for general public awareness.

The following is a link to the National Weather Service’s Hurricane Wind Scale Summary Table. In a nutshell, the categories mean:

Category 1 – Winds: 74 to 95 mph. Storm surge: 4 to 5 feet above normal. Damage primarily to trees and unanchored mobile homes. Some coastal flooding.

Category 2 – Winds: 96 to 110 mph. Storm surge: 6 to 8 feet. Some damage to roofs, doors, windows, trees and shrubbery; flooding damage to piers.

Category 3 – Winds: 111 to 130 mph. Storm surge: 9 to 12 feet. Some structural damage; large trees blown down; flooding near shoreline and possibly inland; mobile homes destroyed.

Category 4 – Winds: 131 to 155 mph. Storm surge: 13 to 18 feet. Extensive damage to doors and windows; major damage to lower floors near shore; terrain may be flooded well inland.

Category 5 – Winds: in excess of 155 mph. Storm surge: more than 18 feet. Complete roof failure and some building failures; massive evacuation. Flooding causes major damage to lower floors of all shoreline buildings.


Be the first to comment - What do you think?  Posted by Admin - 03/29/2011 at 9:37 pm

Categories: Earth Science, Weather   Tags:

How do chlorofluorocarbons (CFCs) affect the ozone layer?

CFCs are hydrocarbons in which some or all of the hydrogen atoms have been replaced by fluorine atoms. They are often used as refrigerants, solvents and until recently as propellants in aerosol cans. When released, they rise high into the Earth’s atmosphere where they interact with the Sun’s ultraviolet rays. Read more…

2 comments - What do you think?  Posted by Admin - 09/18/2010 at 6:13 pm

Categories: Earth Science, Ecology   Tags: ,

How do snowflakes form?

Snowflakes are the result of symmetrical crystallization of water molecules as they turn into ice crystals. Water molecules, when pass to crystalline solid state, such as in ice and snow, form weak bonds (called hydrogen bonds) in which two hydrogen atoms tend to attract neighboring water molecules.

When the temperature drops below the freezing point, the water vapor molecules form hydrogen bonds into a solid state, which exhibits the lowest-energy, an open framework that has a basic symmetrical, hexagonal shape of the snowflake. The higher the symmetry, the more stable the crystal, because this maximizes attractive forces and minimizes the repulsive ones.

The crystallization process is like tiling a floor in accordance with a specific pattern: once the pattern is established and the first tiles are put in place, then all the others go in the predetermined pattern to maintain symmetry. Water molecules simply put themselves to fit the spaces and keep symmetry; this way, the different arms of the snowflake appear.

There are many different types of snowflakes (“no two snowflakes are alike”) because a differentiation occurs due to specific forming circumstances: atmospheric conditions, notably temperature and humidity; and in the atmosphere, where conditions are very complex and variable.

A crystal might begin to grow in one manner and then trasformations in temperature or humidity, after minutes or seconds, change the growth pattern. The hexagonal symmetry prevails, but the ice crystal may form a different branching pattern. The atmosphere changes take place over a large area, so the snowflakes in a region are alike.


1 comment - What do you think?  Posted by Admin - 08/16/2010 at 2:13 am

Categories: Chemistry, Earth Science   Tags:

What is the highest and lowest elevation in the United States?

At 20,320 feet high, Mt. McKinley in Alaska is the highest point in the United States (as well as all of North America). The highest point in the continental United States is Mt. Whitney in California at 14,494 feet. The lowest point is Death Valley, California at 282 feet below sea level. This is also the lowest point in the western hemisphere. Read more…

Be the first to comment - What do you think?  Posted by Admin - 08/08/2010 at 9:13 am

Categories: Earth Science, Geology   Tags: ,

Why is the sea blue?

From The Handy Science Answer Book: there is no single cause for the colors of the sea. It depends in part on when and from where the sea is observed. There are many differing opinions that support almost any explanation. Some explanations include the absorption and scattering of light by pure water; differences caused by suspended matter in sea water; the atmosphere; and even the color and brightness variations of the sky. Read more…

Be the first to comment - What do you think?  Posted by Admin - 07/01/2010 at 11:13 pm

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