Acehtsunami

Tsunamis are unlike wind-generated waves, which many of us may have experiential on a local lake or at a coastal beach, in that they are characterised as shallow-water waves, with long periods and wave lengths. The wind-generated swell one sees at a California beach, for example, spawned by a storm out in the Pacific and metrically rolling in, one wave after another, might have a period of about 10 seconds and a wave length of 150 m. A tsunami, on the other hand, can have a wavelength in excess of 100 km and period on the order of one hour.

As a effect of their long wave lengths, tsunamis behave as shallow-water waves. A wave becomes a shallow-water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the speeding up of gravity (9.8 m/s/s) and the water depth. Let’s see what this implies: In the Pacific Ocean, where the typical water depth is about 4000 m, a tsunami travels at about 200 m/s, or over 700 km/hr. Because the rate at which a wave loses its energy is inversely associated to its wave length, tsunamis not only propagate at high speeds, they can also travel great, transoceanic distances with limited energy losses. The earthquake-generated 1960 Chilean tsunami, for example, travelled across over 17,000 km across the Pacific to hit Japan. The wave crests bend as the tsunami travels —- this is called refraction Wave refraction is caused by segments of the wave moving at different speeds as the water depth along the peak varies.

Bill became the first hurricane of the 2009 Atlantic season as it continued to increase strength, but remain far from any seashore Monday morning..

Claudette, on the other hand, became the first tropical storm to strikes the U.S. mainland this year when it made landfall in the Florida Panhandle early Monday but damaged as it moved farther inland.

By 8 a.m. ET, Claudette had been downgraded to a tropical depression as it moved above Alabama.

Claudette complete landfall about 1:15 a.m. near the eastern end of Santa Rosa Island, just southeast of Fort Walton Beach in Florida..

It is predictable to move into southern Alabama on Monday morning and into northeastern Mississippi by Monday night.

Even before Claudette made landfall, the storm’s outer bands crushed the area with heavy rain, with officials warning that some coastal areas had the possible for localized flooding.

The storm might bring 3 to 6 inches of rain, with some areas getting up to 10 inches across portions of the Florida Panhandle, central and southern Alabama and tremendous southwestern Georgia. Storm surges and isolated tornadoes also were probable across portions of north Florida.

Authorities urge voluntary evacuations in the low-lying Alligator Point area of Florida’s Franklin County since of concerns about possible flooding..

Meanwhile, Hurricane Bill was in the Atlantic heading west-northwest with highest sustained winds of 90 mph.. The storm’s center was about 1,080 miles east of the Lesser Antilles shortly before 11 a.m. ET.

A third weather system, Ana, was downgraded from a tropical storm to a tropical depression.

Ana was about 95 miles southeast of St. Croix early Monday.

It was moving toward the west-northwest near 28 mph, and its maximum continued winds were close to 35 mph…

It was predictable to cross the coast of the Dominican Republic on Monday.

Tsunami are waves caused by unexpected movement of the ocean due to earthquakes, mud slide on the sea floor, land slouch into the ocean, large volcanic eruptions or meteorite collision in the ocean.

Earthquakes:

Most tsunami are caused by large earthquakes on the seafloor when piece of rock move past each other all of the sudden, causing the overlying water to move. The resulting waves move away from the basis of the earthquake event.

Landslides:

Underwater landslides or mud slides can cause tsunami as can global land which slumps into the ocean.

Stages of the landslide tsunami:

1. The red portion of material will become the mud slide and travel down the slope.
2. The material slides down the slope, creating a temporary depression behind it that pulls the water down while at the same time pushing the water in front of it up as it moves forward.
3. The water that was pulled down spreads seaward as the landslide moves further away from the volcano, and the water is pushed up above the sea where the mass of the landslide now lies.
4. The tsunami created by the landslide travels outward completely, creating the large tsunami waves that break on the coast.
5. Finally, the tsunami returns and dies into the open ocean.

Volcanic Eruptions:

Less common are tsunami begin by volcanic eruptions. These occur in several ways:
• Destructive crumple of coastal, island and underwater volcanoes which result in massive landslides;
• Pyroclastic flows, which are thick mixtures of hot blocks, pumice, ash and gas, dropping down volcanic slopes into the ocean and pushing water outwards.
• Like that a caldera volcano collapsing after an eruption causing overlying water to drop rapidly.