Geography of River Deltas - Formation and Importance

Geography of River Deltas - Formation and Importance A river delta is a low-lying plain or landform that occurs at the mouth of a river near where it flows into an ocean or another larger body of water. Deltas greatest importance to human activities, fish and wildlife lay in their characteristic highly fertile soil and dense, diverse vegetation. In order to fully appreciate the role deltas play in our larger ecosystem, it is first important to understand rivers. Rivers are defined as bodies of fresh water generally flowing from high elevations toward an ocean, a lake or another river; sometimes, even back into the ground. Most rivers begin at high elevations where snow, rain, and other precipitation run downhill into creeks and small streams. These small waterways flow ever farther downhill, eventually meeting to form rivers. Rivers flow toward oceans or other larger bodies of water, oftentimes combining with other rivers. Deltas exist as the lowest part of these rivers. It is in these deltas where a rivers flow slows and spreads out to create sediment-rich dry areas and biodiverse wetlands. Formation of River Deltas The formation of a river delta is a slow process. As rivers flow toward their outlets from higher elevations, they deposit mud, silt, sand, and gravel particles at the mouths where rivers and larger, more sedentary bodies of water meet. Over time these particles (called sediment or alluvium) build up at the mouth, extending into the ocean or lake. As these areas continue to grow the water becomes shallower and eventually, landforms begin to rise above the surface of the water, typically elevating to just above sea level. As rivers drop enough sediment to create these landforms or areas of raised elevation, the remaining flowing water with the most power sometimes cuts across the land, forming different branches called distributaries. Once formed, deltas are typically made up of three parts: the upper delta plain, the lower delta plain, and the subaqueous delta. The upper delta plain makes up the area nearest to land. It is usually the area with the least water and highest elevation. The lower delta plain is the middle of the delta. It is a transition zone between the dry upper delta and the wet subaqueous delta. The subaqueous delta is the portion of the delta closest to the sea or body of water into which the river flows. This area is usually past the shoreline and it is below water level. Types of River Deltas Despite the generally universal processes by which river deltas are formed and organized, it is important to note that the worlds deltas vary dramatically in structure, composition, and size due to factors such as origin, climate, geology, and tidal processes. These external factors contribute to an impressive diversity of deltas around the world. A deltas characteristics are classified based upon the specific factors contributing to its rivers deposition of sediment typically the river itself, waves or tides. The main types of deltas are wave-dominated deltas, tide-dominated deltas, Gilbert deltas, inland deltas, and estuaries. As its name would imply, a wave-dominated delta such as the Mississippi River Delta is created by wave erosion controlling where and how much river sediment remains in a delta once it has been dropped. These deltas are usually shaped like the Greek symbol, delta (∆). Tide-dominated deltas such as the Ganges River Delta are formed by tides. Such deltas are characterized by a dendritic structure (branched, like a tree) due to newly-formed distributaries during times of high water. Gilbert deltas are steeper and formed by deposition of coarse material. While it is possible for them to form in ocean areas, their formations are more commonly seen in mountainous areas where mountain rivers deposit sediment into lakes. Inland deltas are deltas formed in inland areas or valleys where rivers may divide into many branches and rejoin farther downstream. Inland deltas, also called inverted river deltas, normally form on former lake beds. Finally, when a river is located near coasts characterized by large tidal variations, they do not always form a traditional delta. Tidal variation often results in estuaries  or a river that meets the sea, such as Saint Lawrence River in Ontario, Quebec, and New York. Humans and River Deltas River deltas have been important to humans for thousands of years because of their extremely fertile soils. Major ancient civilizations grew along deltas such as those of the Nile and the Tigris-Euphrates rivers, with the inhabitants of these civilizations learning how to live with their natural flooding cycles. Many people believe that the ancient Greek historian Herodotus first coined the term delta nearly 2,500 years ago as many deltas are shaped like the Greek delta (∆) symbol. Deltas remain important to humans even today as, among many other things, a source of sand and gravel. Used in highway, building and infrastructure construction, these highly valuable materials quite literally build our world. Delta land is also important in agricultural use. Witness the Sacramento-San Joaquin Delta in California. One of the most agriculturally diverse and productive areas in the state, the region successfully supports numerous crops from kiwi to alfalfa to tangerines. Biodiversity and Importance of River Deltas In addition to (or perhaps in defiance of) these human uses, river deltas boast some of the most biodiverse systems on the planet. As such, it is essential that these unique and beautiful havens of biodiversity remain as healthy habitat for the many species of plants, animals, insects, and fish some rare, threatened or endangered which call them home. In addition to their biodiversity, deltas and wetlands provide a buffer for hurricanes, as open land often stands to weaken the impact of storms as they travel toward larger, more populated areas. The Mississippi River Delta, for example, buffers the impact of potentially strong hurricanes in the Gulf of Mexico.

How to Give an Impromptu Speech (Public Speaking)

How to Give an Impromptu Speech (Public Speaking) An impromptu speech is a speech that you have to make without much or any time to prepare. In life, this can happen when you attend special events, like weddings or celebrations. In school, teachers use impromptu speeches as  homework assignments to help you develop communication skills and to help you prepare for those future life surprises. While this may seem like a cruel trick from a students point of view, it actually builds confidence and is great preparation for life. Rarely will you be asked to stand and deliver a speech with no warning and no time to organize your thoughts. This would be unusual in the classroom unless the teacher is attempting to make a point about the importance of preparedness. At some point in your life, however, you may be asked to speak without notice. There are a few things you can do to avoid panic and embarrassment. Grab a pen and a piece of paper. If you have a few moments before your speech is expected to begin, grab a writing utensil and something to write on, whether its a napkin, envelope, or the back of a receipt you have on hand, and jot down a few thoughts.Highlight a few interesting or significant points.  Keep in mind, your impromptu speech doesnt have to be long. A little-known fact about effective speeches is that if you start with a good line and then end with a really great punch, the speech will  be perceived as a total success. So the beginning and ending markers are critical. The middle portion of your speech should relate to the event youre attending or the class assignment, but if you have to choose one great moment, your ending line is particularly important. If you can walk away gracefully, your speech will be a hit, so keep your big zinger for last.Try to memorize key points. If you have time before your speech, create an outline of the major themes or points and commit it to memory with a memorization trick, like an acronym. Dont try to remember the entire speech in detail like this; just remember important points. Hijack the topic.  There is an old trick that politicians use when theyre being interviewed on TV, and once you realize this, you can use it yourself. They think of questions ahead of time (or topics to discuss), prepare some talking points,  and talk about those, despite the topic or question theyre given. This is a handy trick when youre facing a hard question or asked to discuss a topic with which youre unfamiliar.Remember youre in charge of this time.  Your goal is to deliver a one-sided conversation, off the cuff, so you are in complete control. Relax and make it your own. If you want to make this a funny story about your pesky little brother who always bothers you during homework time, then do it. Everyone will applaud your effort.Feel free to acknowledge that you have not prepared for a speech. If you are speaking in front of friends or family, it may ease your nervousness to express your lack of preparation. This should not be an attempt to garner pity, but rather a way to put yourself and your audience at ease. Then, take a deep breath before you begin speaking. Zone out the audience or choose someone specific to focus on, whichever makes you more comfortable. Begin with your introductory sentence, elaborate, then start working your way to your ending sentence.  Fill in the middle space with as many points as you can, elaborating on each one as you go. Just concentrate on the zinger youve reserved for the end.As you deliver your speech, concentrate on diction and tone.  If you are thinking about this, you wont be thinking about the eyes watching you. Your mind cant think about too many things at once, so think about breathing, enunciating your words, and controlling your tone, and youll maintain more control. What to Do If You Draw a Blank If you suddenly lose your train of thought or draw a complete blank, there are a few you can do to keep from panicking. Pretend youre pausing on purpose. Walk back and forth slowly, as if youre letting your last point sink in.There is always a jokester or friendly person who will stand out in the crowd. Make eye contact and try to draw a response from him or her while you think.If you need more time to think, you may want to ask the audience a question. Have a few prepared ahead, like Do you have any questions, or Can everyone hear me okay?If you still cant remember what you were going to say, make up a reason to pause the speech. You can say, Im sorry, but my throat is very dry. Can I please get a glass of water? Someone will go to get you a drink, and you will have time to think of two or three points to talk about. If these tricks dont appeal to you, think of your own. The goal is to have something ready for every possible scenario ahead of time. If you know you may be asked to give an impromptu speech soon, try going through the entire preparation process with a few common speech topics. When caught off guard, many people can suffer extreme anxiety about speaking off the cuff. Thats why the best speakers are always prepared.