All About Water

Many are unsure of what is on the ocean floor. The ocean floor, also called the seabed or sea floor, is the bottom of the ocean. The ocean floor comprises seventy-one percent of the Earth’s surface.

The Geography of the Ocean

To understand what is on the ocean floor, we must first understand the geography of the rest of the ocean. The geography of the ocean is divided into several levels. Each of these levels has its own typical features based on depth, features like topography, marine life, salinity, and soil composition. The ocean’s levels begin with a continental shelf, a gently sloping area of just around 650 feet deep that surrounds continents. The continental shelf then transitions into a continental slope, a steep descent into the ocean. The continental slope then transitions into the abyssal plain, which begins the seabed.

What Is on the Ocean Floor: The Geography of the Seabed

The breadth of what is on the ocean floor includes plains, enormous undersea mountain ranges called ocean ridges, isolated mountains called seamounts, and more. The deepest parts of the ocean floor are seabed trenches, which are called hadalpelagic trenches. The deepest trench is the Mariana Trench, which measures over 36,000 feet deep—that’s deeper than Mount Everest is tall. The average depth of the ocean, however, is 12,000 feet—that’s about two miles deep.

Life on the Ocean Floor

The soil in seabeds is full of sediment. This sediment collects from rivers, sea currents, magma, and microoganisms’ activity. In recent years we have discovered a variety of marine life in the deep sea, especially around hydrothermal vents.

How We’ve Discovered What Is on the Ocean Floor

For millennia, man has been unable to explore the ocean floor, as the seabed was too deep and pressurized to reach. Because of this, man has long seen the ocean floor as a symbol for mystery and wonder. Fortunately, in recent years we have been able to reach the ocean floor. Scuba divers can now use air tanks to reach shallower parts of the ocean floor. The deepest parts of the ocean floor can be reached with submersibles. Most famously, in 1986, the DSV Alvin explored the seabed wreckage of the Titanic.

How We Monitor What Is on the Ocean Floor

The seabed is always changing. Seafloor spreading continually adds new material to the ocean floor. This is why oceanographers have always wanted to monitor what is on the ocean floor. Sailors used to measure the ocean’s depth by using a lead line, a long piece of rope marked off in fathoms (six-foot intervals) with a weight at one end. The sailors would drop the weighted end into the water, and then the sailors would measure how far the line had entered the ocean when the weight reached the sea floor. In recent years, we have used satellites to map seabed and determine what is on the ocean floor.

Water Clarity

When we think of oceans and lakes, we think of sparkling blue waters. However, upon closer investigation, we see that water is clear.  The reason why water is clear is that it is made up entirely of oxygen and hydrogen.  Because both of these elements are gases, their electrons are unable to absorb or reflect visible light. In fact, water refracts or changes the direction of light. For example, when a T-shirt is soaked with water, it refracts away light, making the object appear darker.  This is why absorbed water darkens material, and why water is clear.

Why Water Is Clear If Ocean and Lake Water Looks Colored

We know how and why water is clear, so it probably doesn’t make immediate sense to us that while a small amount of water is clear, lakes and oceans appear to be blue. The reason for this is that water does not absorb much light, but when it does absorb light, it absorbs red, orange and yellow light.  As a result, it reflects back the shorter blue wavelengths to observers.

Why Water Is Clear: Misleading Opacity

Large bodies of water do not always appear blue.  Many rivers can appear brown, green or even gray. These appearances can be explained by the number of dissolved or suspended particles present in water, and the depth of the water. Both particles and water depth influence how light is reflected or refracted to the observer.  Color variants arise depending on the following circumstances:

• Gray water is generally water that has been stained by runoff from parking lots, buildings and roads in urban areas.
• Brown water is colored by dissolved organic materials like plants and animals.  It is usually found in forests and wetlands.
• Green water is usually stained by suspended particles of living materials, like algae or other microscopic plants.

Why Water Is Clear: Checking for Clarity

If water is clear, there is a much better chance that it is clean.  This is why we must check whether water is turbid or hazy.  We can check water clarify with a Secchi Disk.  This instrument is a black-and-white circular plastic plate that can be lowered into water.  To use a Secchi Disk, first lower it into the water. Stop lowering it when you can’t see it anymore. Next, note the depth (in meters) off of the calibrated line. Then raise the disk back up to where it reappears, again noting the depth off of the calibrated line. Finally, add these two noted depths and divide them by two. This final value can help you gauge water’s clarity. Be sure to compare this value on a weekly basis with measurements at the same lake.

Why does water boil? The answer to the question “Why does water boil” is important knowledge for everyone, as water is part of the basis of human life and provides many health benefits. Boiling water has a number of uses, includingboiling to purify water, sterilizing medical tools, cooking, and as a starting material or solvent in chemical reactions. The boiling point of water and the process of boiling itself is determined by various chemical properties of the substance.

Why Does Water Boil: Boiling Water for Food Preparation

One place to begin investigation of the question “why does water boil” is to survey the most familiar usage of boiling water: food preparation. A variety of simple foods including spaghetti and hard boiled eggs can be prepared simply by placing them in a pot of boiling water. One Food Network show even has the tongue-in-cheek title “How to Boil Water.” With a subject this familiar, a few myths and sayings have naturally arisen. “A watched pot never boils,” says one popular expression. Of course, this is not technically true, an intense gaze having absolutely no effect on the boiling point of water.

Does adding salt to water change anything besides taste?

Something that does affect the boiling point of water, however, is the old tradition of throwing a pinch of salt in the pot. Adding salt to water will raise the boiling point of the water due to the reduction in vapor pressure. This means that the water will boil more slowly, which can be an advantage when trying to hard boil the perfect egg. For an in depth analysis on these effects, referring to Volker Thomsen’s article “The Boiling Point of Water” written for The Physics Teacher may be helpful, or simply just continue reading.

Why Does Water Boil: The Chemistry

When asking why does water boil, people may come across such phrases as “vapor pressure,” “atmospheric pressure,” and “heat of vaporization.” While the boiling point of water is listed as 100 degrees Celsius, the truth is that the boiling point given in the literature is that for standard pressure, approximated as 1 atm.

Why Does Water Boil: More Information on Pressure

But why does water boil at different temperatures depending on the pressure? The short answer is that in order for water to boil, the vapor pressure must be equal to the atmospheric pressure, as molecules are inclined to move from a high pressure to a lower pressure. Though the transition of water from a liquid phase to a gas phase is constantly occurring (think of evaporation), when the vapor pressure of the liquid is lower than the atmospheric pressure, the equilibrium of the process is in favor of the return of the molecule to the liquid phase, or condensation. Boiling, then, occurs when equilibrium favors transition to the gas phase over the vapor phase.

Why Does Water Boil: Boiling Points

When looking at the question of “why does water boil,” it may be interesting to note that water has a higher boiling point and thus takes a longer time to boil than many other liquids such as ethers. Water is made up of a bond of two hydrogen bonds to an oxygen molecule, and as a relatively highly electronegative molecule, oxygen attracts electrons more than hydrogen, creating a partial negative charge on the oxygen molecule and a partial positive on each of the hydrogen molecules. These partial charges mean that the molecule is polar. When this polar molecule is close to other molecules of its kind, hydrogen-hydrogen bonding occurs. These weak bonds may break easily, but breaking these bonds in order to bring all of the molecules into vapor phase requires some additional energy.

Why Does Water Boil: Hydrogen Bonding

The phenomenon of hydrogen bonding is a large contributing factor to the high specific heat of water, 4.18 J/gK. The specific heat is related to how rapidly water can be brought to a boil because it is a measure of how much energy it takes to raise one gram of the substance by one degree Celsius. In more familiar units, it takes one calorie of energy to raise one gram of water by one degree Celsius. Of course, this is the scientific calorie, which is 1/1000 of the food calorie, so just one food calorie could raise one gram (or mL, density of water being 1 g/mL) of water by 1,000 degrees Celsius: good news for cells, which need the energy for metabolism.