What's the difference between an ocean, sea, and saltwater lake?

A simple pictorial explanation of ocean geography

Visualizing ocean geographical features, such as a coastal zone, continental shelf and abyssal plain. This article from the US Geological Survey also provides several links to diverse ocean facts.

The ocean gets its salt from runoff carrying fragments of eroded rock and from seawater dissolving salts and minerals from magma at seafloor spreading centers.

Just as landmasses have been divided into distinct nations, the world ocean has been divided into multiple oceans for various geographical, practical, and scientific reasons.

Earth's oceans do mix, despite viral images and videos claiming to show boundaries between oceans that waters do not cross.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

What animals live in the ocean?

The oceans host an incredible diversity of fascinating species. Oceana's Marine Life Encyclopedia beautifully presents facts and photos of ocean animals from Atlantic Cod to Zebra Sharks.

Although consuming saltwater can dehydrate and kill organisms, some fish survive by using specialized gills that leach excess salt from their bodies back into the surrounding water.

How flooding the Dead Sea could help the climate

There are many dead zones in the world with low elevation and very little rainfall that provide little to no benefits to the ecosystem or climate. This digestible, thorough article explains how piping in nearby water to flood these areas could...

Scientists define sea level as the elevation to which water would settle on Earth's surface, given the planet's gravitational field and rotation.

Why is sea level rising?

Rising global sea level is one of the most commonly cited consequences of climate change, but it’s often unclear how it might affect people living on the coasts. Read this explanation of why global sea level is rising and why sea level rise happens at different rates in different locations.

The Atlantic Ocean was named after Atlas, who holds up the sky in Greek mythology, while the Pacific Ocean was named by Ferdinand Magellan.

The 10 most amazing deep sea creatures

In this video, researchers from the world-renowned Monterey Bay Aquarium discuss the most fascinating deep sea creatures, and how they developed some of their strangest features.

The moon's gravity exerts an overall pressure that displaces the oceans toward the opposite sides of Earth's equator, producing tides.

Salt is harvested from briny ocean water and underground deposits

Mostly sodium chloride, this compound is produced for human use by collecting seawater in shallow pans and allowing the Sun to evaporate the water until crystals remain. Underground rock salt is mined, crushed, and purified from deposits left behind by ancient seas that have dried-up.

Earth's oceans, which have an average depth of 3.7 kilometers (2.3 miles), may be divided into zones based on depth or the abundance of light.

Distinguishing club soda, seltzer, and sparkling water

The three forms of drinking water are similar, but their differences lie mostly in the presence and proportion of minerals and carbonation. Read this quick explainer on the major differences.

Visualizing changes in ocean temperatures between 2016 and 2020

How much does the temperature of the sea change in a given year? This visualization helps illustrate the changes by showing sea surface temperature data from January 2016 through March 2020. Sea surface temperature, which refers to water temperature at the sea's surface, plays a significant role in climate and weather.

An interactive of the deep sea

Desalination involves costly, energy-intensive methods for producing freshwater

Thermal desalination heats saltwater to produce steam, and reverse osmosis forces saltwater through a membrane that only allows water through. In both cases, freshwater is collected and remineralized for consumption, while wastewater brine is often returned to the ocean, where it may harm marine organisms.

38 thought-provoking facts about the ocean

Coral produces its own sunscreen, tsunamis move at 500 miles per hour, one of the loudest sounds ever recorded came from an ice quake, and other interesting facts collected from sources such as National Geographic and NASA.

Explore the deepest parts of the ocean

The deeps of the Earth's oceans are some of the most extreme environments on the planet. Take a trip 36,000 feet to the deepest parts of the sea in this informative, 10-minute animated video.

Hot, semiarid, coastal, cold: An overview of the four desert types

This article describes the various characteristics of deserts, including their geography, their climate, their soil, and the wildlife and vegetation that inhabit them. All desert climates are characterized by extreme temperatures and low rainfall,...

Surface ocean currents are primarily driven by wind, tides, and Earth's rotation, while deep-ocean currents are driven by differences in temperature and salt concentration.

How five of the world's most expensive salt and spices are made

Part of the charm of certain spices and salts is their exotic origin, hailing from difficult-to-access locales or hewn via special processes. That also explains why they can be so expensive. Dive into the businesses of producing and marketing five of the world's most expensive food additives with this engaging video.

Visualizing the 75 largest underwater animals

With so many fish in the sea, which are the largest? This infographic shows fantastic illustrations of the 75 largest sea animals, ranked by average size. The detailed visual is organized in descending order of size, starting with the blue whale,...

Watch a visualization of global ocean currents from NASA's Estimating the Circulation and Climate of the Ocean project.

Watch a visualization of how Earth's oceans impact its atmosphere, weather, and climate.

How salt, sunlight, and wind drive ocean currents

The Atlantic Meridional Overturning Circulation plays a critical role in regulating earth's climate, but is threatened by climate change. Explore the effects of temperature, density, and salinity on ocean currents in this 13-minute PBS video.

Sea stars are invertebrates—they lack a backbone—and while most exhibit pentametric radial symmetry due to having five arms radiating from a central disk, some can possess more than 40.

A chemical overview of water, whose uncommon properties help sustain life on Earth

The uneven distribution of charge in water molecules allows them to bond to each other and to surfaces, enabling them to move against gravity, including up plants through roots and stems. These bonds also keep water in a liquid state over a wider temperature range and make it less dense as it freezes. This causes ice to float and form an insulating layer for underwater ecosystems, from which all life originated.

What's the difference between an ale and a lager?

The major distinction is that ales are typically fruitier, while lagers are cleaner and crisper. This video breaks down several more of the nuanced differences between the two styles.

Sonar, or sound navigation and ranging, uses reflected sound waves to map and detect seafloor features, marine organisms, and other obstacles.

Although an estimated 99.999% of the deep ocean has not been explored, techniques such as sonar have been used to identify the deepest known point in each of Earth's five oceans.

How water pressure affects the body

The extreme conditions of the deep sea include increasing amounts of pressure as explorers and organisms descend into its depths. The major danger for both fish and humans is the way pressure changes how body tissues absorb chemical molecules...

The difference between solstice and equinox, explained

A solstice marks the extremes in the amount of day or night, while the equinoxes come on days with a balance between the two. Learn why with this brief video.

Visualize water's abundance across the solar system, and its relative rarity on Earth

Despite covering almost three-quarters of its surface, water only makes up about 0.12% of Earth's volume. Water in some of Jupiter's and Saturn's moons comprises a larger share of those celestial bodies and of the total water in the solar system. For example, Jupiter's moon Ganymede is believed to harbor almost nine times Earth's oceans beneath its icy shell.

The geoid depicts what Earth would look like if not for tides and currents, given the planet's rotation and uneven gravitational field.

NASA explores Earth's deepest oceans to prepare for space

By studying extreme environments in Earth's hadal zone—the deepest part of the ocean —NASA tests technologies, probes life under crushing pressure, and gathers clues about potential oceans and possible life on worlds like Europa and Enceladus.

Distinguishing the three types of mineral deposits collected via deep-sea mining

The greatest interest is in polymetallic nodules—structures formed from metals in seawater collecting around a core of shell, bone, or rock. Cobalt-rich ferromanganese crusts cover underwater mountain ranges and form over millions of years of metal deposition. Polymetallic sulfide deposits accumulate when seawater seeps into volcanic rocks.

View a gallery of animals found on abyssal plains, hydrothermal vents, seamounts, and other deep-sea habitats.

How the ocean is the new frontier of innovation

Space has been called the final frontier of innovation and investment for decades. Many innovators say the ocean is the new space, the vast majority of whose hidden depths remain obscure. In this podcast episode, business-minded experts discuss the opportunities founders see in the ocean, including seagrass restoration, underwater cable networks, and more.

The Great Lakes hold almost 20% of the world's surface freshwater

Formed by retreating glaciers, the Great Lakes system feeds Niagara Falls through the Niagara River. Together, the lakes contain about 23 quadrillion liters (5,400 cubic miles) of water, enough to cover the land portion of the continental US to a depth of 3 meters (9.84 feet).

Some marine life can survive the extreme pressure of the deep ocean because of specialized molecules that strengthen proteins, enzymes, and cellular membranes.

Moon 101: NASA's complete overview of our lunar companion

From modulating our tides to impact our climate, Earth's lone natural satellite plays a key role forming the planet's habitat. Before diving into the rest of the resources on this page, check out NASA's overview of the basics of the Moon—how it got its name, its size and distance from Earth, its structure, and much more.

Understanding the stages of sleep

Do you have trouble keeping the different stages of sleep straight and organized in your mind? Us too. Sometimes it helps to have a straightforward listing of what each stage is and why it’s important. Look no further than this resource from Lumen. It is a basic outline of the four stages of the sleep cycle, along with the brainwaves and attributes that characterize each. If you’re brave enough, test yourself on the built-in quiz!

Take an interactive dive and see the animals that populate the oceans, from coral near the surface to shrimp-like organisms near the seafloor.

It's called kosher salt because it works for curing kosher meat

Kosher foods align with Jewish religious customs based on scripture. While there is a type of salt that is kosher (most often, salts without iodine), the kosher salt you see around the US is actually big, flaky salts used in a kosher process of curing meats.

NOAA's interactive sea level rise viewer

How will rising seas affect you? Launch NOAA's sea level rise viewer and zoom in on impacts to different parts of the United States, or type in your city or address to learn more.

Underwater nighttime photos capture the ocean's diversity

Self-taught photographer Steven Kovacs explores Palm Beach's ocean after sunset, capturing tiny sea creatures in deep waters. Over eight years, he's dived into Florida's eastern coast, drifting from 0 to 100 feet, photographing rarely seen larval fish. Lacking formal marine biology training, Kovacs collaborates globally to identify species like cusk eels and the female blanket octopus, known for its revealing membrane. Check out his photos here.

The Southern Ocean features the Antarctic Circumpolar Current—the largest ocean current on Earth—which encircles Antarctica and creates a unique biogeographical zone.