People have been making maps for thousands of years. One of the oldest known maps was found near the city of Kirkuk, Iraq. Most geographers say it dates from 2500 BCE. It is a palm-sized block of clay depicting an area with two hills and a stream. (Some geographers think the stream is a canal made by people for irrigation.) Geographers have identified one of the towns on the map. However, they are not sure exactly what the hand-held map represents.
Ancient maps could also be quite large. A nine-foot wall painting in Catal Hyuk, Turkey, was made about 6000 BCE. It is a map of a busy city, complete with crowded housing and even an erupting volcano. However, some scientists believe this "map" is decorative and not an accurate representation of what was there.
The American aviator Douglas Corrigan is often nicknamed "Wrong-Way Corrigan" because of a navigational error he made on a flight in 1938. Corrigan had just piloted a very impressive flight from Long Beach, California, to New York, New York. He was scheduled to fly back to Long Beach. Instead, with the sky covered in clouds, Wrong Way Corrigan flew to Dublin, Ireland.
A gazetteer is a geographic dictionary. Gazetteers, which have existed for thousands of years, usually contain some sort of map and a set of information. Some gazetteers may contain a list of capital cities or areas where a specific resource is found. Other gazetteers may contain information about the local population, such as languages spoken, money used, or religious beliefs.
Geography is the study of places and the relationships between people and their environments. Geographers explore both the physical properties of Earth’s surface and the human societies spread across it. They also examine how human culture interacts with the natural environment, and the way that locations and places can have an impact on people. Geography seeks to understand where things are found, why they are there, and how they develop and change over time.
The term "geography" comes to us from the ancient Greeks, who needed a word to describe the writings and maps that were helping them make sense of the world in which they lived. In Greek, geo means “earth” and -graphy means “to write.” Using geography, Greeks developed an understanding of where their homeland was located in relation to other places, what their own and other places were like, and how people and environments were distributed. These concerns have been central to geography ever since.
Of course, the Greeks were not the only people interested in geography. Throughout human history, most societies have sought to understand something about their place in the world, and the people and environments around them.
Indeed, mapmaking probably came even before writing in many places. But ancient Greek geographers were particularly influential. They developed very detailed maps of areas in and around Greece, including parts of Europe, Africa, and Asia. More importantly, they also raised questions about how and why different human and natural patterns came into being on Earth’s surface, and why variations existed from place to place. The effort to answer these questions about patterns and distribution led them to figure out that the world was round, to calculate Earth’s circumference, and to develop explanations of everything from the seasonal flooding of the Nile River to differences in population densities from place to place.
During the Middle Ages, geography ceased to be a major academic pursuit in Europe. Advances in geography were chiefly made by scientists of the Muslim world, based around the Arabian Peninsula and North Africa. Geographers of this Islamic Golden Age created the world’s first rectangular map based on a grid, a map system that is still familiar today. Islamic scholars also applied their study of people and places to agriculture, determining which crops and livestock were most suited to specific habitats or environments.
In addition to the advances in the Middle East, the Chinese empire in Asia also contributed immensely to geography. Until about 1500, China was the most prosperous civilization on Earth. The Chinese were scientifically advanced, especially in the field of astronomy. Around 1000, they also achieved one of the most important developments in the history of geography: They were the first to use the compass for navigational purposes. In the early 1400s, the explorer Cheng Ho embarked on seven voyages to the lands bordering the China Sea and the Indian Ocean, establishing China’s dominance throughout Southeast Asia.
Age of Discovery
Through the 13th-century travels of the Italian explorer Marco Polo, Europeans learned about the riches of China. Curiosity was awakened; a desire to trade with wealthy Asian cultures motivated a renewed interest in exploring the world. The period of time between the 15th and 17th centuries is known in the West as the Age of Exploration or the Age of Discovery.
With the dawn of the Age of Discovery, the study of geography regained popularity in Europe. The invention of the printing press in the mid-1400s helped spread geographic knowledge by making maps and charts widely available. Improvements in shipbuilding and navigation facilitated more exploring, greatly improving the accuracy of maps and geographic information.
Greater geographic understanding allowed European powers to extend their global influence. During the Age of Discovery, European nations established colonies around the world. Improved transportation, communication, and navigational technology allowed countries such as the United Kingdom to successfully govern colonies as far away as the Americas, Asia, Australia, and Africa.
Geography was not just a subject that made colonialism possible, however. It also helped people understand the planet on which they lived. Not surprisingly, geography became an important focus of study in schools and universities.
Geography also became an important part of other academic disciplines, such as chemistry, economics, and philosophy. In fact, every academic subject has some geographic connection. Chemists study where certain chemical elements, such as gold or silver, can be found. Economists examine which nations trade with other nations, and what resources are exchanged. Philosophers analyze the responsibility people have to take care of the Earth.
Emergence of Modern Geography
Some people have trouble understanding the complete scope of the discipline of geography because, unlike most other disciplines, geography is not defined by one particular topic. Instead, geography is concerned with many different topics—people, culture, politics, settlements, plants, landforms, and much more.
What distinguishes geography is that it approaches the study of diverse topics in a particular way (that is, from a particular perspective). Geography asks spatial questions—how and why things are distributed or arranged in particular ways on Earth’s surface. It looks at these different distributions and arrangements at many different scales. It also asks questions about how the interaction of different human and natural activities on Earth’s surface shape the characteristics of the world in which we live.
Geography seeks to understand where things are found and why they are present in those places; how things that are located in the same or distant places influence one another over time; and why places and the people who live in them develop and change in particular ways. Raising these questions is at the heart of the “geographic perspective.”
Exploration has long been an important part of geography. But exploration no longer simply means going to places that have not been visited before. It means documenting and trying to explain the variations that exist across the surface of Earth, as well as figuring out what those variations mean for the future.
The age-old practice of mapping still plays an important role in this type of exploration, but exploration can also be done by using images from satellites or gathering information from interviews. Discoveries can come by using computers to map and analyze the relationship among things in geographic space, or from piecing together the multiple forces, near and far, that shape the way individual places develop.
Applying a geographic perspective demonstrates geography’s concern not just with where things are, but with “the why of where”—a short, but useful definition of geography’s central focus.
The insights that have come from geographic research show the importance of asking “the why of where” questions. Geographic studies comparing physical characteristics of continents on either side of the Atlantic Ocean, for instance, gave rise to the idea that Earth’s surface is comprised of large, slowly moving plates—plate tectonics.
Studies of the geographic distribution of human settlements have shown how economic forces and modes of transport influence the location of towns and cities. For example, geographic analysis has pointed to the role of the U.S. Interstate Highway System and the rapid growth of car ownership in creating a boom in U.S. suburban growth after World War II. The geographic perspective helped show where Americans were moving, why they were moving there, and how their new living places affected their lives, their relationships with others, and their interactions with the environment.
Geographic analyses of the spread of diseases have pointed to the conditions that allow particular diseases to develop and spread. Dr. John Snow’s cholera map stands out as a classic example. When cholera broke out in London, England, in 1854, Snow represented the deaths per household on a street map. Using the map, he was able to trace the source of the outbreak to a water pump on the corner of Broad Street and Cambridge Street. The geographic perspective helped identify the source of the problem (the water from a specific pump) and allowed people to avoid the disease (avoiding water from that pump).
Investigations of the geographic impact of human activities have advanced understanding of the role of humans in transforming the surface of Earth, exposing the spatial extent of threats such as water pollution by manmade waste. For example, geographic study has shown that a large mass of tiny pieces of plastic currently floating in the Pacific Ocean is approximately the size of Texas. Satellite images and other geographic technology identified the so-called “Great Pacific Garbage Patch.”
These examples of different uses of the geographic perspective help explain why geographic study and research is important as we confront many 21st century challenges, including environmental pollution, poverty, hunger, and ethnic or political conflict.
Because the study of geography is so broad, the discipline is typically divided into specialties. At the broadest level, geography is divided into physical geography, human geography, geographic techniques, and regional geography.
The natural environment is the primary concern of physical geographers, although many physical geographers also look at how humans have altered natural systems. Physical geographers study Earth’s seasons, climate, atmosphere, soil, streams, landforms, and oceans. Some disciplines within physical geography include geomorphology, glaciology, pedology, hydrology, climatology, biogeography, and oceanography.
Geomorphology is the study of landforms and the processes that shape them. Geomorphologists investigate the nature and impact of wind, ice, rivers, erosion, earthquakes, volcanoes, living things, and other forces that shape and change the surface of the Earth.
Glaciologists focus on the Earth’s ice fields and their impact on the planet’s climate. Glaciologists document the properties and distribution of glaciers and icebergs. Data collected by glaciologists has demonstrated the retreat of Arctic and Antarctic ice in the past century.
Pedologists study soil and how it is created, changed, and classified. Soil studies are used by a variety of professions, from farmers analyzing field fertility to engineers investigating the suitability of different areas for building heavy structures.
Hydrology is the study of Earth’s water: its properties, distribution, and effects. Hydrologists are especially concerned with the movement of water as it cycles from the ocean to the atmosphere, then back to Earth’s surface. Hydrologists study the water cycle through rainfall into streams, lakes, the soil, and underground aquifers. Hydrologists provide insights that are critical to building or removing dams, designing irrigation systems, monitoring water quality, tracking drought conditions, and predicting flood risk.
Climatologists study Earth’s climate system and its impact on Earth’s surface. For example, climatologists make predictions about El Nino, a cyclical weather phenomenon of warm surface temperatures in the Pacific Ocean. They analyze the dramatic worldwide climate changes caused by El Nino, such as flooding in Peru, drought in Australia, and, in the United States, the oddities of heavy Texas rains or an unseasonably warm Minnesota winter.
Biogeographers study the impact of the environment on the distribution of plants and animals. For example, a biogeographer might document all the places in the world inhabited by a certain spider species, and what those places have in common.
Oceanography, a related discipline of physical geography, focuses on the creatures and environments of the world’s oceans. Observation of ocean tides and currents constituted some of the first oceanographic investigations. For example, 18th-century mariners figured out the geography of the Gulf Stream, a massive current flowing like a river through the Atlantic Ocean. The discovery and tracking of the Gulf Stream helped communications and travel between Europe and the Americas.
Today, oceanographers conduct research on the impacts of water pollution, track tsunamis, design offshore oil rigs, investigate underwater eruptions of lava, and study all types of marine organisms from toxic algae to friendly dolphins.
Human geography is concerned with the distribution and networks of people and cultures on Earth’s surface. A human geographer might investigate the local, regional, and global impact of rising economic powers China and India, which represent 37 percent of the world’s people. They also might look at how consumers in China and India adjust to new technology and markets, and how markets respond to such a huge consumer base.
Human geographers also study how people use and alter their environments. When, for example, people allow their animals to overgraze a region, the soil erodes and grassland is transformed into desert. The impact of overgrazing on the landscape as well as agricultural production is an area of study for human geographers.
Finally, human geographers study how political, social, and economic systems are organized across geographical space. These include governments, religious organizations, and trade partnerships. The boundaries of these groups constantly change.
The main divisions within human geography reflect a concern with different types of human activities or ways of living. Some examples of human geography include urban geography, economic geography, cultural geography, political geography, social geography, and population geography. Human geographers who study geographic patterns and processes in past times are part of the subdiscipline of historical geography. Those who study how people understand maps and geographic space belong to a subdiscipline known as behavioral geography.
Many human geographers interested in the relationship between humans and the environment work in the subdisciplines of cultural geography and political geography.
Cultural geographers study how the natural environment influences the development of human culture, such as how the climate affects the agricultural practices of a region. Political geographers study the impact of political circumstances on interactions between people and their environment, as well as environmental conflicts, such as disputes over water rights.
Some human geographers focus on the connection between human health and geography. For example, health geographers create maps that track the location and spread of specific diseases. They analyze the geographic disparities of health-care access. They are very interested in the impact of the environment on human health, especially the effects of environmental hazards such as radiation, lead poisoning, or water pollution.
Specialists in geographic techniques study the ways in which geographic processes can be analyzed and represented using different methods and technologies. Mapmaking, or cartography, is perhaps the most basic of these. Cartography has been instrumental to geography throughout the ages.
As early as 1500 BCE, Polynesian navigators in the Pacific Ocean used complex maps made of tiny sticks and shells that represented islands and ocean currents they would encounter on their voyages. Today, satellites placed into orbit by the U.S. Department of Defense communicate with receivers on the ground called global positioning system (GPS) units to instantly identify exact locations on Earth.
Today, almost the entire surface of Earth has been mapped with remarkable accuracy, and much of this information is available instantly on the internet. One of the most remarkable of these websites is Google Earth, which “lets you fly anywhere on Earth to view satellite imagery, maps, terrain, 3D buildings, from galaxies in outer space to the canyons of the ocean.” In essence, anyone can be a virtual Christopher Columbus from the comfort of home.
Technological developments during the past 100 years have given rise to a number of other specialties for scientists studying geographic techniques. The airplane made it possible to photograph land from above. Now, there are many satellites and other above-Earth vehicles that help geographers figure out what the surface of the planet looks like and how it is changing.
Geographers looking at what above-Earth cameras and sensors reveal are specialists in remote sensing. Pictures taken from space can be used to make maps, monitor ice melt, assess flood damage, track oil spills, predict weather, or perform endless other functions. For example, by comparing satellite photos taken from 1955 to 2007, scientists from the U.S. Geological Survey (USGS) discovered that the rate of coastal erosion along Alaska’s Beaufort Sea had doubled. Every year from 2002 to 2007, about 45 feet per year of coast, mostly icy permafrost, vanished into the sea.
Computerized systems that allow for precise calculations of how things are distributed and relate to one another have made the study of geographic information systems (GIS) an increasingly important specialty within geography. Geographic information systems are powerful databases that collect all types of information (maps, reports, statistics, satellite images, surveys, demographic data, and more) and link each piece of data to a geographic reference point, such as geographic coordinates. This data, called geospatial information, can be stored, analyzed, modeled, and manipulated in ways not possible before GIS computer technology existed.
The popularity and importance of GIS has given rise to a new science known as geographic information science (GISci). Geographic information scientists study patterns in nature as well as human development. They might study natural hazards, such as a fire that struck Los Angeles, California, in 2008. A map posted on the internet showed the real-time spread of the fire, along with information to help people make decisions about how to evacuate quickly. GIS can also illustrate human struggles from a geographic perspective, such as the interactive online map published by the New York Times in May 2009 that showed building foreclosure rates in various regions around the New York City area.
The enormous possibilities for producing computerized maps and diagrams that can help us understand environmental and social problems have made geographic visualization an increasingly important specialty within geography. This geospatial information is in high demand by just about every institution, from government agencies monitoring water quality to entrepreneurs deciding where to locate new businesses.
Regional geographers take a somewhat different approach to specialization, directing their attention to the general geographic characteristics of a region. A regional geographer might specialize in African studies, observing and documenting the people, nations, rivers, mountains, deserts, weather, trade, and other attributes of the continent. There are different ways you can define a region. You can look at climate zones, cultural regions, or political regions. Often regional geographers have a physical or human geography specialty as well as a regional specialty.
Regional geographers may also study smaller regions, such as urban areas. A regional geographer may be interested in the way a city like Shanghai, China, is growing. They would study transportation, migration, housing, and language use, as well as the human impact on elements of the natural environment, such as the Huangpu River.
Whether geography is thought of as a discipline or as a basic feature of our world, developing an understanding of the subject is important. Some grasp of geography is essential as people seek to make sense of the world and understand their place in it. Thinking geographically helps people to be aware of the connections among and between places and to see how important events are shaped by where they take place. Finally, knowing something about geography enriches people’s lives—promoting curiosity about other people and places and an appreciation of the patterns, environments, and peoples that make up the endlessly fascinating, varied planet on which we live.
Term Part of Speech Definition Encyclopedic Entry academic Adjective
person or thing having to do with school, particularly college or university education.
condition of being exact or correct.
to accomplish or attain.
Age of Exploration Noun
(1400s-1800s) period during which Europeans traveled the world by ocean in search of trade.
the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).
Encyclopedic Entry: agriculture algae Plural Noun
(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.
to study in detail.
an underground layer of rock or earth which holds groundwater.
Encyclopedic Entry: aquifer astronomy Noun
the study of space beyond Earth's atmosphere.
layers of gases surrounding a planet or other celestial body.
Encyclopedic Entry: atmosphere biogeography Noun
study of the spatial patterns of living organisms.
to exist on the edge of a boundary.
to reach a conclusion by mathematical or logical methods.
art and science of making maps.
physical, cultural, or psychological feature of an organism, place, or object.
type of map with information useful to ocean or air navigators.
Encyclopedic Entry: chart chemistry Noun
study of the atoms and molecules that make up different substances.
mainly or essentially.
infectious, sometimes fatal disease that harms the intestines.
Christopher Columbus Noun
(1446-1506) Italian navigator.
distance around the outside of a circle.
complex way of life that developed as humans began to develop urban settlements.
Encyclopedic Entry: civilization climate Noun
all weather conditions for a given location over a period of time.
Encyclopedic Entry: climate climatology Noun
study of the Earth's atmosphere.
coastal erosion Noun
wearing away of earth or sand on the beach by natural or man-made methods.
people and land separated by distance or culture from the government that controls them.
sharing of information and ideas.
instrument used to tell direction.
Encyclopedic Entry: compass comprise Verb
to contain or be made up of.
a disagreement or fight, usually over ideas or procedures.
person who uses a good or service.
one of the seven main land masses on Earth.
Encyclopedic Entry: continent coordinates Noun
a set of numbers giving the precise location of a point, often its latitude and longitude.
Encyclopedic Entry: crop cultural geographer Noun
person who studies the relationship between learned behavior of human beings, including language and religion, and the places humans live.
learned behavior of people, including their languages, belief systems, social structures, institutions, and material goods.
desire to know more about a subject.
steady, predictable flow of fluid within a larger body of that fluid.
Encyclopedic Entry: current dam Noun
structure built across a river or other waterway to control the flow of water.
data Plural Noun
(singular: datum) information collected during a scientific study.
a collection of information for analysis and interpretation.
having to do with the social characteristics and statistics of a population.
number of things of one kind in a given area.
Encyclopedic Entry: density desert Noun
area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.
Encyclopedic Entry: desert disease Noun
a harmful condition of a body part or organ.
to divide and spread out materials.
to keep track of.
authority or control.
very expressive or emotional.
period of greatly reduced precipitation.
Encyclopedic Entry: drought Earth Noun
our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.
Encyclopedic Entry: Earth earthquake Noun
the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity.
branch of biology that studies the relationship between living organisms and their environment.
Encyclopedic Entry: ecology economics Noun
study of monetary systems, or the creation, buying, and selling of goods and services.
chemical that cannot be separated into simpler substances.
El Nino Noun
irregular, recurring weather system that features a warm, eastern-flowing ocean current in the eastern Pacific Ocean.
Encyclopedic Entry: El Niño embark Verb
to leave or set off on a journey.
group of nations, territories or other groups of people controlled by a single, more powerful authority.
person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).
person who starts and manages a business.
conditions that surround and influence an organism or community.
to wear away.
act in which earth is worn away, often by water, wind, or ice.
Encyclopedic Entry: erosion ethnic Adjective
having to do with characteristics of a group of people linked by shared culture, language, national origin, or other marker.
to leave or remove from a dangerous place.
person who studies unknown areas.
to enlarge or continue.
to help or make easier.
person who cultivates land and raises crops.
capacity of soil to sustain plant growth; or the average number of children born to women in a given population.
Encyclopedic Entry: fertility foreclosure Noun
process where a building owner is unable to pay their creditors, so the creditors may sell the building.
person who studies places and the relationships between people and their environments.
geographic information science (GISci) Noun
study of distribution and patterns in nature and human development using technology and research.
geographic information system (GIS) Noun
any system for capturing, storing, checking, and displaying data related to positions on the Earth's surface.
Encyclopedic Entry: GIS (geographic information system) geographic perspective Noun
a way to understand a topic or area using spatial features and relationships.
geographic techniques Plural Noun
ways in which geographic processes can be analyzed and represented using different methods and technologies.
study of places and the relationships between people and their environments.
Encyclopedic Entry: geography geomorphology Noun
study of geographic features on the landscape and the forces that create them.
having to do with geography and location.
study of glaciers and ice sheets.
Global Positioning System (GPS) Noun
system of satellites and receiving devices used to determine the location of something on Earth.
valuable chemical element with the symbol Au.
to make public-policy decisions for a group or individuals.
system or order of a nation, state, or other political unit.
ecosystem with large, flat areas of grasses.
Great Pacific Garbage Patch Noun
area of the North Pacific Ocean where currents have trapped huge amounts of debris, mostly plastics.
Encyclopedic Entry: Great Pacific Garbage Patch grid Noun
horizontal and vertical lines used to locate objects in relation to one another on a map.
Gulf Stream Noun
warm current that starts in the Gulf of Mexico and travels along the eastern coast of the U.S. and Canada before crossing the North Atlantic Ocean.
environment where an organism lives throughout the year or for shorter periods of time.
Encyclopedic Entry: habitat hazard Noun
danger or risk.
human geography Noun
the study of the way human communities and systems interact with their environment.
the need for food.
the study of water.
large chunks of ice that break off from glaciers and float in the ocean.
Encyclopedic Entry: iceberg insight Noun
vast, worldwide system of linked computers and computer networks.
watering land, usually for agriculture, by artificial means.
Encyclopedic Entry: irrigation Islamic Golden Age Noun
(600-1200) time period when science and art flourished in north Africa and the Middle East, where the Islamic religion is widely practiced.
body of water surrounded by land.
specific natural feature on the Earth's surface.
Encyclopedic Entry: landform lava Noun
molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.
chemical element with the symbol Pb.
livestock noun, plural noun
animals raised for sale and profit.
symbolic representation of selected characteristics of a place, usually drawn on a flat surface.
Encyclopedic Entry: map Marco Polo Noun
(1254-1324) Italian explorer.
marine organism Noun
living creature with an ocean habitat.
central place for the sale of goods.
Middle Ages Noun
(500-1500) period in European history between the Roman Empire and the Renaissance.
Middle East Noun
region of southwest Asia and northeast Africa.
movement of a group of people or animals from one place to another.
Muslim world Noun
countries with a majority Muslim population, mostly located in the Middle East and North Africa.
art and science of determining an object's position, course, and distance traveled.
Encyclopedic Entry: navigation oceanography Noun
study of the ocean.
Encyclopedic Entry: oceanography offshore Adjective
having to do with facilities or resources located underwater, usually miles from the coast.
oil rig Noun
complex series of machinery and systems used to drill for oil on land.
oil spill Noun
accidental release of petroleum products into a body of water, either by an oil tanker or an offshore oil rig.
sudden occurrence or rapid increase.
process of too many animals feeding on one area of pasture or grassland.
unique or special.
arrangement of people, places, or things across a specific space.
study of soil.
permanently frozen layer of the Earth's surface.
Encyclopedic Entry: permafrost perspective Noun
representation of volume or depth on a flat surface.
an unusual act or occurrence.
the study of the basic principles of knowledge.
physical geography Noun
study of the natural features and processes of the Earth.
plate tectonics Noun
movement and interaction of the Earth's plates.
political geography Noun
study of the spatial relationships that influence government or social policies.
art and science of public policy.
introduction of harmful materials into the environment.
Encyclopedic Entry: pollution Polynesia Noun
island group in the Pacific Ocean between New Zealand, Hawaii, and Easter Island.
status of having very little money or material goods.
energy, emitted as waves or particles, radiating outward from a source.
regional geography Noun
branch of geography devoted to the study of characteristics of a specific region.
a system of spiritual or supernatural belief.
available supply of materials, goods, or services. Resources can be natural or human.
object that orbits around something else. Satellites can be natural, like moons, or made by people.
satellite imagery Noun
photographs of a planet taken by or from a satellite.
extent or width.
period of the year distinguished by special climatic conditions.
Encyclopedic Entry: season seasonal flooding Noun
overflowing of a body of water from its banks, usually predicted by yearly rains or storms.
chemical element with the symbol Ag.
top layer of the Earth's surface where plants can grow.
having to do with location and placement.
exact or precise.
the collection and analysis of sets of numbers.
field of study within a larger area of research.
geographic area, mostly residential, just outside the borders of an urban area.
a study or analysis of characteristics of an area or a population.
the science of using tools and complex machines to make human life easier or more profitable.
degree of hotness or coldness measured by a thermometer with a numerical scale.
Encyclopedic Entry: temperature tide Noun
rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.
Encyclopedic Entry: tide toxic Adjective
buying, selling, or exchanging of goods and services.
movement of people or goods from one place to another.
movement from one place to another.
ocean waves triggered by an earthquake, volcano, or other movement of the ocean floor.
United Kingdom Noun
nation made of the countries of England, Wales, Scotland, and Northern Ireland.
having to do with city life.
urban area Noun
developed, densely populated area where most inhabitants have nonagricultural jobs.
Encyclopedic Entry: urban area USGS Noun
(United States Geological Survey) primary source for science about the Earth, its natural and living resources, natural hazards, and the environment.
Encyclopedic Entry: USGS variation Noun
an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.
Encyclopedic Entry: volcano voyage Noun
long journey or trip.
water cycle Noun
movement of water between atmosphere, land, and ocean.
Encyclopedic Entry: water cycle water pollution Noun
introduction of harmful materials into a body of water.
water quality Noun
chemical, physical, and biological characteristics of water for a specific purpose such as drinking.
state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.
Encyclopedic Entry: weather 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.
World War II Noun
(1939-1945) armed conflict between the Allies (represented by the United States, the United Kingdom, and the Soviet Union) and the Axis (represented by Germany, Italy, and Japan.)