Answers To Exploration Guide On Tides
The regular rise and fall of the ’s waters are known as s. Along s, the water slowly rises up over the and then slowly falls back again. When the water has risen to its highest level, covering much of the shore, it is. When the water falls to its lowest level, it is. Some s and s can also have tides. Causes of Tides Forces that contribute to tides are called s.
The Earth’s is a tidal constituent. The major tidal constituent is the ’s on the Earth.
The closer objects are, the greater the gravitational force is between them. Although the sun and moon both gravitational force on the Earth, the moon’s pull is stronger because the moon is much closer to the Earth than the sun is. The moon’s ability to raise tides on the Earth is an example of a. The moon exerts a tidal force on the whole. This has little effect on Earth’s land surfaces, because they are less flexible. Land surfaces do move, however, up to 55 centimeters (22 inches) a day.
These movements are called s. Terrestrial tides can change an object’s. Terrestrial tides are important for and calculating on a. S study terrestrial tides because this movement in the Earth’s can sometimes trigger a. The moon’s tidal force has a much greater effect on the surface of the ocean, of course. Water is and can respond to more ally.
High Tides The tidal force exerted by the moon is strongest on the side of the Earth facing the moon. It is weakest on the side of the Earth facing the opposite direction. These differences in gravitational force allow the ocean to bulge outward in two places at the same time. One bulge occurs on the side of the Earth facing the moon.
This is the moon’s direct tidal force pulling the ocean toward it. The other bulge occurs on the opposite side of the Earth. Here, the ocean bulges in the opposite direction of the moon, not toward it. The bulge may be understood as the moon’s tidal force pulling the planet (not the ocean) toward it. These bulges in the ocean waters are known as high tides.
The high tide on the side of the Earth facing the moon is called the. The high tide caused by the bulge on the opposite side of the Earth is called the. In the open ocean, the water bulges out toward the moon. Along the seashore, the water rises and spreads onto the land. Low Tides and Ebb Tides One high tide always faces the moon, while the other faces away from it. Between these high tides are areas of lower water levels—low tides.
The flow of water from high tide to low tide is called an. Most tides are, which means they take place twice a day. For example, when an area covered by the ocean faces the moon, the moon’s gravitational force on the water causes a high high tide.
As the Earth rotates, that area moves away from the moon’s influence and the tide ebbs. Now it is low tide in that area. As the Earth keeps rotating, another high tide occurs in the same area when it is on the side of the Earth opposite the moon (low high tide). The Earth continues spinning, the tide ebbs, another low tide occurs, and the cycle (24 hours long) begins again. The vertical difference between high and low tide is called the. Each month, the range changes in a regular pattern as a result of the sun’s gravitational force on the Earth.
Although the sun is almost 390 times farther away from the Earth than is the moon, its high still affects the tides. Because the Earth’s surface is not, tides do not follow the same patterns in all places. The shape of a seacoast and the shape of the ocean floor both make a difference in the range and frequency of the tides. Along a smooth, wide beach, the water can spread over a large area. The tidal range may be a few centimeters. In a confined area, such as a narrow, rocky or, the tidal range could be many meters.
The lowest tides are found in enclosed s like the Mediterranean or the Baltic. They rise about 30 centimeters (about a foot). The largest tidal range is found in the Bay of Fundy, Canada. There, the tides rise and fall almost 17 meters (56 feet). Twice each month, the moon lines up with the Earth and sun. These are called the and the full moon.
When the moon is between the Earth and the sun, it is in the sun’s shadow and appears dark. This is the new moon. When the Earth is between the sun and moon, the moon reflects sunlight. This is the full moon.
When the sun, moon and Earth are all lined up, the sun’s tidal force works with the moon’s tidal force. The combined pull can cause the highest and lowest tides, called s.
Spring tides happen whenever there is a new moon or a full moon and have nothing to do with the season of spring. (The term comes from the German word springen, which means “to jump.”) In the period between the two spring tides, the moon faces the Earth at a right angle to the sun. When this happens, the pull of the sun and the moon are weak. This causes tides that are lower than usual.
These tides are known as s. Tidal Features Tides produce some interesting features in the ocean.
Tides are also associated with features that have nothing to do with them. A occurs along a coast where a river empties into the ocean or sea. The tidal bore is a strong tide that pushes up the river, against the river's current. This is a true tidal wave. The huge tidal bore of the Amazon River is called the. The pororoca is a wave up to 4 meters (13 feet) tall, traveling at speeds of 15 kilometers (9 miles) per hour.
The pororoca travels 10 kilometers (6 miles) up the Amazon. While a tidal bore is a tidal wave, a is not. Tsunami is taken from the Japanese words for “harbor wave.” Tsunamis are caused not by tides, but by underwater s and es. Tsunamis are associated with tides because their reach es the tidal range of an area.
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So-called “s” also have nothing to do with actual tides. A red tide is another term for an.
Are sea creatures. When billions of red algae form, or “bloom,” in the ocean, the waves and tides appear red.
Finally, s are not a tidal feature. Rip tides are strong ocean s running along the surface of the water. A rip tide runs from the shore back to the open ocean. Rip tides can be helpful to surfers, who use them to avoid having to paddle out to sea.
Rip tides can also be very dangerous to swimmers, who can be swept out to sea. Intertidal Life The land in the tidal range is called the. The intertidal zone is often marked by s. Tide pools are areas that are completely underwater at high tide but remain as pockets of seawater when the tide ebbs. Tide pools are home to some of the ocean’s richest. The intertidal zone can be. A zone with a hard bottom is rocky.
A zone with a soft bottom has. S and es are often soft-bottomed intertidal zones. Different creatures have ed to different types of intertidal zones. Hard-bottom zones often have barnacles and s, while soft-bottom zones have more sea plants and slow-moving creatures like s.
Intertidal zones are marked. Different organisms live in different zones in the tidal range, depending on how much water reaches them. This zonation can often be seen vertically, with dry plants near the top of the tidal zone and seaweeds near the bottom. The intertidal zone can be broken into four major mini-zones. The highest is called the (1).
This area is splashed by water and during high tide, but is never fully underwater. Barnacles live on rocks in the splash zone. Many s, such as seals and sea otters, can live in the splash zone. The (2) is pounded by strong waves. Animals that live in the high-tide zone often have strong s and are able to cling tightly to rocks to avoid being swept out to sea.
These animals include mussels and barnacles. Crabs, which have tough s and can hide under rocks, also live in the high-tide zone. The (3) is usually the busiest part of the intertidal zone.
This is where tide pools usually form. Animals from the high- and low-tide zones come here to feed. Animals that live in the mid-tide zone are still tough, but can have softer bodies than their neighbors in the high-tide zone. Brightly colored s, which are soft-bodied but strongly ed to rocks, live in tide pools.
Snails and s use shells to protect their soft bodies. S (sometimes called starfish, although they are not related to fish at all) are perfectly adapted to life in tide pools. They have a tough, leathery body that can withstand strong tides and s. They have thousands of tiny, tube-like legs that help them stick to rocks or put them on the move for.
Sea stars are s, and will eat anything, such as fish, snails, or crabs. They especially love mussels. The way sea stars eat is unusual. Sea stars move over a mussel and use their arms to pry open the mussel’s shell. Then, the sea star s its own to surround the mussel. The sea star’s stomach contains powerful s that the mussel and make it easy to when the sea star pulls its stomach back into its body.
The (4) is only dry at the lowest tide. S, a type of sea slug, live in tide pools in the low-tide zone. Like the sea star, this animal is a carnivore. Nudibranchs eat sponges, barnacles and other nudibranchs. Nudibranchs can also eat sea anemones, because they are immune to its s. People can be very active in the low-tide zone.
Simple nets can catch fish here, and fishers can collect animals like crabs, mussels, and clams. “The tide is out, our table is set,” is a traditional saying among the Tlingit nation , who live along the Pacific Northwest coast in Alaska and Canada. In the low-tide zone of the Puget Sound in the U.S. State of Washington, people practice tidal. Aquaculture is the breeding, raising, and harvesting of plants and animals that live in the water. One of the most harvested animals is a giant clam called a.
Geoduck farms have been set up in the Puget Sound tidelands, which are areas covered by the intertidal zone. On the farms, geoducks live in plastic pipes. Environmental groups worry about the impact of these pipes on the environment. Tools of aquaculture, such as unsecured pipes, nets, and rubber bands, can be washed away by tides. This can the ocean, and natural tide pools.
Tides and People Tidal energy is a that many s and s hope will be developed on a large scale. Now, small programs in Northern Ireland, South Korea, and the U.S. State of Maine are experimenting with ing the power of tides.
There are three different types of tidal power. All of these use s to convert that power into for use in homes and. In most tidal energy generators, turbines are put in s (1). A is a machine that takes energy from a flow of. That fluid can be air or liquid (water).
Because water is more than air, tidal energy is more powerful than. Placing turbines in tidal streams can be difficult, because the machine s the tide it is trying to harness. However, once the turbines are in place, tidal energy is predictable and.
Another tidal energy generator uses a type of called a (2). A barrage is a low dam where water can spill over the top or through turbines in the dam.
Barrages can be ed across tidal rivers and estuaries. Turbines inside the barrage can harness the power of tides the same way a dam can harness the power of a river.
Barrages are more designs than single turbines. The final type of tidal energy generator is a (3).
The lagoons function much like barrages, but are usually constructed out of more natural materials, like rocks. Tidal lagoons can sit along coasts and do not prevent the natural of. Geographic imaging systems (GIS) rely on tidal calculations. GIS must account for tides when, especially when mapping the ocean floor.
Tides affect the report on an area’s depth. Ing tides is very important for and travel across oceans. Ships decide which s they may by calculating their own weight, the depth of the ocean and an area’s tidal range.
Errors in navigation can strand ships along shores or on s. Can sit and while waiting for a tide. This was not a problem after the 2004 tsunami in Southeast Asia. Even though the tsunami destroyed kilometers of coastline, GIS helped disaster-relief agencies get aid to victims in Indonesia, Thailand, and Sri Lanka. Term Part of Speech Definition Encyclopedic Entry acid Noun chemical compound that reacts with a base to form a salt. Acids can corrode some natural materials. Acids have pH levels lower than 7.
Adapt Verb to adjust to new surroundings or a new situation. Algae Plural Noun (singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds. Algal bloom Noun the rapid increase of algae in an aquatic environment. Anchor Verb to hold firmly in place.
Aquaculture Noun the art and science of cultivating marine or freshwater life for food and industry. Barrage Noun a low dam. Bay Noun body of water partially surrounded by land, usually with a wide mouth to a larger body of water. Beach Noun narrow strip of land that lies along a body of water. Biodiversity Noun all the different kinds of living organisms within a given area. Canal Noun artificial waterway. Cargo Noun goods carried by a ship, plane, or other vehicle.
Carnivore Noun organism that eats meat. Celestial Adjective having to do with the sky or heavens.
Channel Noun waterway between two relatively close land masses. Coast Noun edge of land along the sea or other large body of water. Complex Adjective complicated. Construct Verb to build or erect.
Consumer Noun person who uses a good or service. Coordinates Noun a set of numbers giving the precise location of a point, often its latitude and longitude. Crust Noun rocky outermost layer of Earth or other planet. Current Noun steady, predictable flow of fluid within a larger body of that fluid.
Dam Noun structure built across a river or other waterway to control the flow of water. Debris Noun remains of something broken or destroyed; waste, or garbage. Dense Adjective having parts or molecules that are packed closely together. Digest Verb to convert food into nutrients that can be absorbed.
Disrupt Verb to interrupt. Dissolve Verb to break up or disintegrate. Dramatic Adjective very expressive or emotional. Earthquake Noun the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity.
Ebb tide Noun tide that flows from high tide to low tide. Eject Verb to get rid of or throw out.
Electricity Noun set of physical phenomena associated with the presence and flow of electric charge. Engineer Noun person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).
Estuary Noun mouth of a river where the river's current meets the sea's tide. Exert Verb to force or pressure.
Exoskeleton Noun the hard external shell or covering of some animals. Fluid Noun material that is able to flow and change shape. Geoduck Noun type of large, burrowing clam. Geographic information system (GIS) Noun any system for capturing, storing, checking, and displaying data related to positions on the Earth's surface. Global Positioning System (GPS) Noun system of satellites and receiving devices used to determine the location of something on Earth.
Gravitational pull Noun physical attraction between two massive objects. Gravity Noun physical force by which objects attract, or pull toward, each other. Hard-bottomed Adjective shore or coast with a rocky lower layer. Harness Verb to control or guide for a specific purpose. Hermit crab Noun type of marine animal (crustacean) that uses found materials, such as other creatures' shells, as its shell. High high tide Noun tide created when the Earth directly faces the moon.
High tide Noun water level that has risen as a result of the moon's gravitational pull on the Earth. High-tide zone Noun coastal area that is partially submerged at high tide. Industry Noun activity that produces goods and services. Inlet Noun small indentation in a shoreline.
Intertidal zone Noun region between the high and low tide of an area. Lake Noun body of water surrounded by land. Liquid Noun state of matter with no fixed shape and molecules that remain loosely bound with each other. Location Noun position of a particular point on the surface of the Earth. Low high tide Noun tide created when the Earth faces away from the moon.
Low tide Noun water level that has dropped as a result of the moon's gravitational pull on the Earth. Low-tide zone Noun mostly submerged coastal area that is only exposed at low tide. Mapping Noun making and using maps.
Marine mammal Noun an animal that lives most of its life in the ocean but breathes air and gives birth to live young, such as whales and seals. Marsh Noun wetland area usually covered by a shallow layer of seawater or freshwater. Mass Noun unit of measurement (abbreviated m) determined by an object's resistance to change in the speed or direction of motion.
Microscopic Adjective very small. Mid-tide zone Noun coastal area that is underwater at high tide, partially submerged as the tide ebbs, and exposed at low tide. Migration Noun movement of a group of people or animals from one place to another. Mist Noun clouds at ground-level, but with greater visibility than fog. Moon Noun natural satellite of a planet.
Navigate Verb to plan and direct the course of a journey. Neap tide Noun the lowest level of high tide when the difference between low and high tide is the least, occurring when the gravitational pull of the sun counteracts that of the moon. New moon Noun dark phase of the lunar cycle when the moon is invisible or barely visible, occurring when the moon passes between the sun and earth.
Nudibranch Noun brightly colored marine organism (gastropod), also called a sea slug. Ocean Noun large body of salt water that covers most of the Earth. Planet Noun large, spherical celestial body that regularly rotates around a star. Poisonous Adjective toxic or containing dangerous chemicals.
Pollute Verb to introduce harmful materials into a natural environment. Pororoca Noun local term for tidal bore, or tidal wave, especially of the Amazon River.
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Precise Adjective exact. Predator Noun animal that hunts other animals for food. Predict Verb to know the outcome of a situation in advance.
Prey Noun animal that is hunted and eaten by other animals. Radio astronomy Noun the study of outer space using radio waves.
Ray Noun flat-bodied fish with fins that appear to flap like wings. Red tide Noun the rapid, dense accumulation of algae or other plankton that contain red or brown pigments; also called algal bloom. Renewable resource Noun resource that can replenish itself at a similar rate to its use by people. Rip tide Noun strong current that runs along the surface of the ocean from shore to open sea. Also called rip current.
River Noun large stream of flowing fresh water. Rotation Noun object's complete turn around its own axis.
Sand Noun small, loose grains of disintegrated rocks. Sand bank Noun large underwater deposit of sand, often tall enough to reach the water's surface. Sea Noun large part of the ocean enclosed or partly enclosed by land.
Sea anemone Noun type of marine animal related to corals and jellies. Sea star Noun marine animal (echinoderm) with many arms radiating from its body. Also called a starfish. Seaweed Noun marine algae.
Seaweed can be composed of brown, green, or red algae, as well as 'blue-green algae,' which is actually bacteria. Semidiurnal Adjective occuring twice a day. Shell Noun hard outer covering of an animal. Shipping Noun transportation of goods, usually by large boat. Shore Noun coast. Significant Adjective important or impressive.
Silt Noun small sediment particles. Soft-bottomed Adjective shore or coast with a soft lower layer of silt or sand. Splash zone Noun coastal area above the high-tide zone that is only submerged during storms. Spoil Verb to rot or ruin. Spring tide Noun tide occuring during the times of full and new moon that 'springs' to above-average highs and lows. Stable Adjective steady and reliable.
Starfish Noun sea star. Marine animal with multiple arms that can cling to rocks or move about. Sea stars are not fish.
Stomach Noun organ in animals that helps digest food. Surfing Noun the sport of riding down a breaking wave on a board.
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Surpass Verb to go beyond a set limit. Technology Noun the science of using tools and complex machines to make human life easier or more profitable. Tentacle Noun a long, narrow, flexible body part extending from the bodies of some animals. Terrestrial tide Noun the effect of the moon's tidal force on land surfaces of the Earth. Tidal bore Noun tidal wave. Tide flowing upstream against the current of a river, forming a wave of water.
Tidal constituent Noun force that helps create a tide. Tidal energy Noun energy produced as ocean waters surge in and out with tides.
Tidal energy generator Noun machine for turning tidal energy into electricity humans can use. Tidal flat Noun coastal wetlands, often found within the intertidal zone, formed when mud is deposited by tides. Tidal force Noun gravitational pull exerted by one object, such as the sun or moon, that raises tides on another object, such as the Earth. Tidal lagoon Noun pool of ocean water that is partially cut off from the ocean by a barrier. Often used as a source of hydroelectric power. Tidal range Noun the difference in height between an area's high tide and low tide.
Tidal stream Noun an ocean current produced by the tide. Tide Noun rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.
Tidelands Noun intertidal zone. Region between the high tide and the low tide of an area. Tide pool Noun small pond created by an ebb tide and submerged by a high tide. Tribe Noun community made of one or several family groups sharing a common culture. Tsunami Noun ocean waves triggered by an earthquake, volcano, or other movement of the ocean floor. Turbine Noun machine that captures the energy of a moving fluid, such as air or water. Uniform Adjective exactly the same in some way.
Vertical zonation Noun the arrangement of species adapted to different, layered areas of a larger ecosystem. Volcanic eruption Noun activity that includes a discharge of gas, ash, or lava from a volcano.
Volcano Noun an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions. Volcanologist Noun scientist who studies volcanoes. Wave Noun moving swell on the surface of water.
Wetland Noun area of land covered by shallow water or saturated by water. Wildlife Noun organisms living in a natural environment.
Wind Noun movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun. Wind energy Noun kinetic energy produced by the movement of air, able to be converted to mechanical power.
Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited. Writers Kim Rutledge Melissa McDaniel Diane Boudreau Tara Ramroop Santani Teng Erin Sprout Hilary Costa Hilary Hall Jeff Hunt Illustrators Tim Gunther Mary Crooks, National Geographic Society Editors Kara West Jeannie Evers, Emdash Editing Educator Reviewer Nancy Wynne Producer Caryl-Sue, National Geographic Society Sources Dunn, Margery G. (1989, 1993). 'Exploring Your World: The Adventure of Geography.' Washington, D.C.: National Geographic Society. Last Updated June 23, 2011.
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