How To Understand Natural Disasters
Unless we have been living in total seclusion and without the benefit of any form of communication of late, we have all become aware of the occurrences of some of nature’s most devastating upheavals or disasters. Many agree that there is a “top ten list” of these naturally occurring events, most of which are weather related, that include landslides/avalanches, droughts, heat waves/blizzards, wildfires, floods, tsunamis, volcanic eruptions, tornadoes, earthquakes, and hurricanes. Whether we were personally affected by the recent serious earthquake in Mexico or were in the path of one or more of the most recent hurricanes, we certainly have a family member, a friend or know of someone affected by these events and perhaps prayed for their safety and wellbeing.
It would be wonderful if one could just look up: “what causes earthquakes?” and the answer would be perfectly clear to anyone who had an interest. However, it is a bit more involved than that since it is “science” after all! When searching for information about earthquakes you will find terms such as “faults,“ “tectonic plates,” “lithosphere” and “asthenosphere,” to name a few. Simply put (hopefully), the top crusty layer of the earth, called the “lithosphere” exists as separate and distinct “tectonic plates” which float on a fluid-like “asthenosphere” layer. The sheer fluidity of the asthenosphere layer may allow the tectonic plates to undergo motion in different directions. A ”fault,” also known as a fracture occurs when the blocks of crust on either side of it have moved, relative to one another and parallel to the fracture, so that when underground rock suddenly breaks along the fault it causes a sudden release of energy leading to seismic waves that cause the earth to shake and you now have an earthquake! At this point, dependent upon the level of the seismic activity one may just feel a little tremor, note things moving around on shelves, hear glass breaking, feel the ground “breaking” apart or, hopefully, watch from a distance as structures lean, break apart and fall to the ground.
It is important to note that just because natural disasters are listed as separate entities does not mean that they always occur independently of one another, as one incident can set off one or more of the other phenomenon. It has been estimated that there are approximately 500,000 earthquakes that occur each year, 100,00 of which can actually be felt. Approximately 90% of earthquakes each year occur within the Pacific Ring of Fire, an area of almost 25,000 miles that forms an arc around the Pacific Ocean where more than 452 volcanoes are located. Seismic activity is prevalent under both the land’s and the ocean’s tectonic plates, and in addition to producing to earthquakes can lead to volcanic eruptions, landslides, avalanches, tsunamis, etc. Although earthquakes are “natural” events some can be “man-made” as in the case of building dams heavy with water, drilling (and now fracking), injecting liquid into the ground and erecting tall heavy buildings.
Hurricanes, cyclones, and typhoons all come under the general heading of “tropical cyclones” and are all just different names for a similar weather event, depending upon where they occur, but are considered to be the most violent storms on earth. If you have never been out of the United States then you have only been exposed to either North Atlantic or East Pacific hurricanes. In South East Asia, North East Australia and the South Pacific Islands you will find cyclones and while in Japan I personally experienced a typhoon. However, we do understand violent storms as we have recently been dealing with Harvey, Irma and Maria, just the latest in a series of Atlantic storms or hurricanes that have left devastation behind in parts of Texas and Louisiana, the United States East Coast, Puerto Rico and many of the Caribbean Islands along the way.
From an Atlantic perspective, the area that runs along latitudes that are 50 on either side of the equator, located between South America and Africa is part of the Intertropical Convergent Zone (ITCZ), which is often referred to as the doldrums. It can be quite calm at the ITCZ as that is where the two belts of trade winds meet and essentially neutralize each other, but it is also the common source for waves that can signal the formation of a new tropical storm. Both Harvey and Irma developed from tropical waves off the West African coast and Maria was formed from a tropical wave just east of the Lesser Antilles, a chain of islands north of Venezuela in South America.
Like giant engines, hurricanes need warm, moist air for fuel which is why they form only over the warm ocean waters near the equator. Since the waters off the west coast of Africa are kept warm by the heat of the Sahara Desert, what better place than that for a tropical wave to be turned into a full-blown problem. In the formation process, warm, moist air over the ocean surface rises upward causing an area of lower air pressure to form below so that more higher-pressure air from surrounding areas can push into it, only for it to also rise once it too becomes warm and moist causing more surrounding air to swirl in while the water that is now in the air forms clouds. The whole system of clouds and wind continues to spin and grow, fed by the ocean's heat and the water evaporating from the ocean’s surface and as this continues a calm eye forms into which more high-pressure air flows. Storms that form north of the equator spin counterclockwise while storms south of the equator spin clockwise due to Earth's rotation on its axis.
A hurricane goes through many stages as it develops starting as a westward-moving area of low pressure or tropical wave and as the system of thunderclouds, rain, and gusty winds continue to form it becomes a tropical disturbance. As the air pressure continues to drop and the winds are sustained up to 38 mph it is then a tropical depression and when the winds reach between 39 to 73 mph we have a tropical storm, but when those winds get up to 74 mph it is truly a hurricane. Beyond that, the hurricane increases to a Category 2 at 95 mph, a Category 3 at 111 mph, a Category 4 at 131 mph and finally, a Category 5 at 155 mph. Tropical hurricanes usually weaken once they hit land because they are no longer being "fed" by the energy from the warm ocean waters. However, they can continue to move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.
As in the instance of earthquakes, there are several other potential consequences of hurricanes, starting with the aforementioned wind and rain. Tornadoes are frequently associated with hurricanes and depending on the velocity of the wind, anything that is not tied down has the potential to become a flying missile, from relatively small patio chairs to automobiles and even large boats. In the case of Irma, prior to its arrival in Florida, the tides were out as much as three feet beyond normal, but upon the hurricane’s arrival, the wind motion brought the water back in a surge flooding the coastal areas. Essentially the same thing happens along coastal areas, only to a greater degree, when tsunamis are formed, as in the recent happening when massive amounts of materials, or debris, was moved from the shores of Japan to the coastal areas of our state of Washington.
When it comes to natural disasters there is nothing we can do to stop them if they are truly natural and not a man-made. All we can do is the effort we make to erect structures that can withstand earthquakes and hurricanes. Nature is usually calm and beautiful, but it obviously has its moments of rebellion!