All About Water

Natural Disasters

Natural disasters are a natural hazards that causes human loss. Just a few natural disasters include hydrological disasters, earthquakes, and volcanic eruptions.

What Is a Natural Disaster?

A natural disaster is a natural hazard, but a natural hazard is not necessarily a natural disaster. A natural disaster becomes a natural hazard when it occurs near vulnerable human populations. Natural disasters kill people and cause financial damage. For example, an earthquake that strikes an uninhabited place is a natural hazard, but not a natural disaster because it doesn’t kill people or destroy human property. An earthquake that strikes San Francisco, however, is a natural disaster. The amount of damage that a natural disaster creates depends on people’s resilience, their ability to withstand and resist the disaster. Natural disasters come in a variety of forms.

Hydrological Disasters

Hydrological disasters are natural disasters caused by water. Hydrological disasters include floods, tropical cyclones, and tsunamis. Floods are often created by tropical cyclones, which produce storm surge. Tsunamis are caused by underwater earthquakes. Japan’s 2011 Tohoku earthquake and accompanying tsunami is estimated to have killed up to 25,000 people.

Earthquakes

An earthquake is a shaking of the Earth’s crust that happens when tectonic plates collide. These shakings differ in magnitude depending on the force of the tectonic plates’ collision. The underground place where the tectonic plates collide is called the “focus.” The point directly above the focus, which suffers the most damage, is called the “epicenter.” An earthquake alone won’t usually kill people or wildlife. However, earthquakes usually trigger secondary events that do cause damage. Earthquakes make buildings collapse and cause fires and tsunamis. These secondary events are what cause earthquakes to be perceived as natural disasters.  Societies can lessen their vulnerability to earthquakes by monitoring underground activity, warning people when earthquakes are going to occur, planning evacuations, and by building safer buildings and safety systems.

Volcanic Eruptions

Volcanic eruptions can destroy their surroundings in several ways. The initial volcanic explosion can produce dangerous rock falls. The lava produced by volcanic eruptions may trickle down, destroying nearby buildings and plants. Volcanic eruptions also produce toxic ash clouds, which can settle over nearby places. Even the smallest quantities of ash are toxic if inhaled, and enough ash can collapse roofs. The most destructive part of a volcanic eruption is pyroclastic flows, collections of hot volcanic ash clouds that rush down slopes. Historians believe that pyroclastic flows destroyed Pompeii. Volcanic eruptions, however, are some of the most visually astounding kinds of natural disasters.

The xylem and phloem are the two kinds of tissues that transport water and other nutrients within plants. The xylem carries water up through the plant. The phloem transports nutrients, most notably glucose, down throughout the plant.

Xylem and Phloem: The Xylem

In Classical Greek, “xylem” translates to “wood.” This makes sense, as the most common xylem tissue is wood. The xylem supply all of the parts of a plant with water by transporting water up through the plant. Xylem are long tubes called vessels. They pump water from the roots up, replacing the water that plants lose to transpiration and photosynthesis.

Xylem and Phloem: How the Xylem Transport Water

Plants depend on xylem to replace the water that evaporates off of their leaves. The xylem can transport their sap through transpirational pull. In transpirational pull, water transpires, or evaporates, off of plant surfaces into the atmosphere. As transpiration pulls water out of the plant, the water tension within the plant pulls water from the plant’s roots and soil back into the leaves. This water tension is strong enough to lift water hundreds of meters above the ground into the highest branches of trees. However, for transpirational pull to work, the xylem vessels must be very compact in diameter, as this compactness maximizes pressure.

Xylem and Phloem: Other Ways That the Xylem Transport Water

The xylem can also pull water and nutrients up through the plant via root pressure. Through osmosis, plants absorb water into their roots. This osmosis then forces sap up the xylem and into the leaves. The xylem are also aided by capillary action, the force by which water adheres to the surface of xylem pipes. This capillary action balances gravity.

Xylem and Phloem: How the Phloem Work

Phloem is the second transporting tissue in vascular plants. The phloem carry nutrients, most notably glucose, down throughout the plant. Like “xylem,” “phloem” derives from Ancient Greek. “Phloem” translates to “bar,” which makes sense, as phloem is the innermost layer of bark in trees. Phloem transport the nutrients that plants produce in photosynthesis. The phloem’s transportation is called translocation. Translocation moves the phloem’s sugar-rich sap from sugar sources to sugar sinks. Plants generally store their sugars in their roots, and the phloem transports sugar from the roots to the growing areas in the plant, the sugar sink.

Differences Between the Xylem and Phloem

The xylem and phloem both transport vital commodities through plants. However, the xylem and phloem differ in several ways. While the xylem transport mostly water, the phloem transport nutrients, especially glucose. The xylem are made up of dead cells, while the phloem are made up of living cells. Xylem only transport sap upward, while the phloem are multidirectional—they move sugars wherever they’re needed. To work, the xylem rely on water tension, while the phloem rely on translocation.

All About Bubbles

A bubble is a globule of one thermodynamic phase inside of another, like a gas in a liquid. We commonly find bubbles in boiling water, carbonated sodas, sea foam, and gas pockets in glass. Learning about bubbles can teach us about many concepts, like shape, transparency, mirrored surfaces, colors, and flexibility.

About Bubbles: How Bubbles Form

Bubbles are produced by the scientific process of nucleation. Nucleation occurs when a small pocket of one thermodynamic phase forms inside of another. In bubbles, the thermodynamic phase of a gas forms inside of the thermodynamic phase of a liquid. However, pure water is not stable enough to produce a lingering bubble. We use soap to stabilize bubbles, allowing them to linger for longer. Many incorrectly believe that soap increases water’s surface tension. This is not true. In fact, soap decreases water’s surface tension. Soap does not strengthen bubbles, it merely stabilizes them.

About Bubbles: How We Use Bubbles

We use bubbles in many ways, both practical and fun. We use bubbles in ultrasounds to help us better see babies. We use bubbles to better understand mathematical concepts, like minimal surface area. Performance artists use bubbles for their aesthetic properties. We also use bubbles as toys. Children have been playing with bubbles since the 1600s. Toy stores sell about two hundred million bottles of bubble mixture every year.

About Bubbles: Why Bubbles Pop

When disturbed, bubbles pulsate, or rapidly oscillate in size. These oscillations destabilize bubbles, leading them to eventually tear apart. The popping of bubbles below produces most of the liquid sounds that we hear.

About Bubbles: Make Your Own Bubbles

If you would like to learn more about bubbles, you can do so by observing them yourself. Enjoy educational, fun homemade bubbles by mixing your own bubble solution. Simply combine ½ a cup of dishwashing liquid, two teaspoons of sugar, and two cups of water to make bubbles whenever you want.

What Are Introduced Species?

Introduced species are species that now live outside of their native range. These species are introduced to new areas–usually over previously inaccessible bodies of water–by human activity, either deliberately or accidentally. The Environmental Protection Agency defines introduced species as “species that have become able to survive and reproduce outside the habitats where they evolved or spread naturally.”

The Terminology of Introduced Species

Scientists are ambivalent about introducing species to areas that they don’t naturally inhabit. Introduced species are introduced to these new areas by accidental or deliberate human activity. Introduced species can harm the ecosystems of the places that they’re introduced to. However, sometimes introduced species can have no effect on or even help the ecosystems they’re introduced to. For instance, some of the plants that Europeans brought into North America have aided the continent’s biodiversity and productivity. Because introduced species can spread too quickly for us to control and can sometimes help us, most environmentalists consider it impractical and undesirable to simply prohibit introducing non-native species.

How We Refer to Introduced Species

Scientists refer to introduced species by many terms, like “non-indigenous,” “non-native,” “exotic,” and even “invasive.” The broadest term applied to introduced species is “non-native,” which can be applied to both agriculturally maintained and wild species. Some introduced species can survive by themselves in nature when introduced—these are “naturalized” species. “Invasive” species threaten ecosystems by spreading or reproducing too widely or too fast, thereby harming the environment or human health.

How We Introduce Species: Intentionally Introduced Species

Through human activity, we introduce species to places that they don’t naturally inhabit. Sometimes we introduce species accidentally, and sometimes intentionally. People usually introduce species intentionally because they will economically gain by doing so. For instance, New Zealand introduced the Monterey Pine to bolster timber crops. We have also introduced species for recreational activities, like game hunting or ornamental gardening. We have also introduced species by bringing pets overseas. When we try to establish introduce these species in the wild, we often have trouble predicting how well the introduced species will fare. For this reason, we often have to make several attempts to establish an introduced species.

Accidentally Introduced Species

Sometimes people accidentally introduce species to new areas. For example, we have spread many rat species spread across the world by unintentionally transporting them aboard ships. Human travel also introduces several species to places where they don’t naturally inhabit. For example, tourists introduced the African killer bee to Brazil.

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.

The Science and Story of Rainbows 

Rainbows fascinate us. We find them in nature, and then expound upon and replicate them in our religions, mythologies, literature, art, and music. In this article we will talk about the science of rainbows, our cultural perception of rainbows, and we will learn how to make a rainbow.

How to Make a Rainbow: What Is A Rainbow?

The bright rainbows that we see in the sky are “primary rainbows,” which are red on the outside of their arcs and violet on the inside. They are caused by the light that is reflected from water droplets. Although we artificially subdivide rainbows into “bands,” the colors present in rainbows are not actually separate from each other. A rainbow is a continuous spectrum of colors. Infamous “double rainbows” appear as a color-inverted second arc above a primary rainbow. Rumored “triple rainbows” are scientifically impossible and cannot naturally occur.

How to Make a Rainbow: Where Do We Find Rainbows?

We can find rainbows wherever we find sunlight shining through airborne water droplets at a low angle. We can find rainbows around rainclouds, waterfalls, and fountains. We perceive rainbows to be brightest when half of the sky is still dark with rainclouds. Sometimes, when the moon is bright enough, we can even find moonbows, or nighttime rainbows. Interestingly, one cannot actually be “under” or “at the end of” a rainbow: even if you are looking at someone who appears to be at the end of a rainbow, from their vantage point, the person sees the rainbow as being still further off yet. This means that rainbows are not actual, physical objects that we can physically approach. So much for pots of gold.

How to Make a Rainbow: Rainbows in Science

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.

What Are Tide Pools?

Tide pools are little seawater-filled craters that form by oceans. Often these tide pools are indiscernible during the parts of the day when they are covered with seawater. They separate only at low tide, when they are revealed as microcosmic ecosystems. Naturalists and philosophers alike are fascinated by tide pools because of their scale. As John Steinbeck once wrote, “It is advisable to look from the tide pool to the stars and then back to the tide pool again.” Naturalists are also fascinated by the hardiness of the animals that live within tide pools. These animals must adapt to their environment, which changes daily.

Life in Tide Pools

Tide pool ecosystems are constantly changing. The saltiness, oxygen levels and temperature of the tide pool’s water changes every day. Because of this, only the hardiest organisms, like barnacles, can survive in tide pools. These inhabitants must survive the midday sun, big waves and predators. Tide pool creatures must be able to withstand these changing pressures. Ironically, however, they also rely on the tide pool’s changeability—their greatest danger—to survive. The fresh water provides tide pool inhabitants with fresh food sources.

Tide Pools: Microcosmic Ecosystems

Tide pools form small food chains unto themselves. Starfish eat mussels, which eat plants. Even within themselves, tide pools can be subdivided into smaller regions, or zones.

Tide Pools: The Spray Zone

The spray zone, the area highest up in the tide pool, is constantly bombarded with spray from tides and storms. This part of the tide pool is the most exposed to the elements, like the sun and winds.  For this reason, the spray zone is the most difficult area for creatures to survive. It is sparsely populated by only the hardiest creatures, like barnacles, whose impenetrable shells protect them from the elements.

Tide Pools: The High Tide Zone

The high tide zone is the part of the tide pool that is immersed in water only during high tide. While this area is easier to survive than the spray zone, the animals that live within it must still survive an ever-changing environment of waves and sunlight. In the high tide zone one can find crabs, anemones, and mussels. Although waves make life difficult in the high tide zone, they also bring food to its inhabitants.

Tide Pools: The Low Tide Zone

The low tide zone is submerged in water almost all day. This regularizes sunlight exposure and water’s saltiness and provides more shelter for the low tide zone’s dwellers. This easier survival allows for more biodiversity. The low tide zone is populated by more aquatic marine vegetation (seaweeds) than the other zones. Here one can find shrimp and sea cucumbers.

What Is Salt Marsh?

Salt marsh is an ecosystem that occurs between land and saltwater, an ecosystem that helps protect the coast. Salt marshes are populated by salt-tolerant plants like herbs, grasses and shrubs. These plants allow the salt marsh to trap sediment. The salt marsh then exports these nutrients to the coast. Salt marsh also creates a habitat for land-bound animals like mammals and migratory birds.

Where Do We Find Salt Marsh?

Salt marsh occurs on temperate coasts in sheltered environments like estuaries and embankments. In tropical areas, salt marsh is replaced by mangroves, marshes populated by salt-tolerant trees instead of salt-tolerant herbs. Salt marsh frequently occurs along the deltas of large rivers, like the Mississippi.

Salt Marsh is Unique

Unlike land-bound habitats, coastal salt marsh ecosystems are flooded by tidal flow every day. This tidal flow helps deliver sediments to salt marsh. The nutrients that collect in salt marshes make them highly productive environments that enable a broad food chain of organisms. In salt marshes we can find everything from bacteria to mammals. However, to survive, salt marsh organisms must be tolerant of salinity and flooding. Flora further inland are less exposed to salinity and flooding, and therefore don’t usually need to be as hardy, allowing inland salt marsh flora more diversity.

How Humans Have Harmed Salt Marsh

People flock to salt marshes for their beauty and coastal location. In 2002, over half of the world’s population lived within thirty-five miles of the coast. However, our population density along coasts means that we greatly impact salt marshes, often in negative ways. In the past people perceived marshlands as near-wasteland, and we used “land reclamation” to convert these areas into upland for agricultural purposes. After that, this upland was sometimes again converted into urban or industrial land, as in the cities of Boston and Tokyo. We have polluted salt marsh with runoff and nitrogen loading, introducing new species while killing off old ones. However, by altering marshlands, we have altered the salt marsh ecosystem. We’ve devastated salt marshes’ biodiversity and natural water flow.

Salt Marsh Perception and Restoration

Nowadays people are trying to restore salt marsh and reverse land reclamation. People no longer perceive salt marshes as “coastal wastelands,” and now see how biologically productive these areas are. In terms of biodiversity, people now perceive salt marshes as similar to tropical rainforests. Legislation such as the United States’ Clean Water Act now protects salt marsh habitats.

A body of water (or “water body”) is a pool of water that covers the Earth. The term “body of water” usually refers to large pools of water like seas, lakes and oceans, but it can also refer to smaller pools, like ponds, tide pools, and even puddles.

Various Bodies of Water

There are many, many different types of bodies of water. Some bodies of water occur naturally. Others, like reservoirs and harbors, are man-made. Although water formations that move around, like rivers and streams, aren’t always considered bodies of water, there is no other English term for moving bodies of water, so they are typically grouped with other bodies of water. Some bodies of water are less well-known and culturally and geographically limited in scope. For instance, the Spanish have named the “arroyo,” a creek that temporarily fills with water after a heavy rain or a rainy season. The Australians have named the “billabong,” a pool of water that forms when a river changes its course. Some major bodies of water include oceans, seas, and rivers.

Major Bodies of Water: Oceans

The largest bodies of water are oceans, enormous pools of saltwater. Oceans are continuous bodies of water that divide into smaller seas. Although interconnected, we typically describe oceans as separate. Earth’s oceans run about two miles deep. They are home to about 230,000 known marine species, and perhaps ten times that number of unknown marine species. Although interconnected into one global saltwater body that oceanographers sometimes call the “World Ocean,” Earth’s oceans are usually described as five separate bodies of water. This allows us to specify which part of the World Ocean we’re talking about. These five oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean, and the Arctic Ocean.

Major Bodies of Water: Seas

Seas are large bodies of water that are usually connected with oceans. The term “sea” is sometimes incorrectly used as a synonym for the term “ocean.” However, oceanographers see seas and oceans as two different kinds of bodies of water. Seas are smaller saltwater bodies that are usually interconnected with oceans, but can sometimes be disconnected from oceans. For instance, the Caspian Sea is in fact a saltwater lake.

Major Bodies of Water: Rivers

Rivers are moving, usually freshwater bodies of water. They typically flow into other bodies of water, like oceans, seas, lakes, and other rivers. However, they can sometimes flow into the ground or dry up before reaching other bodies of water.