American oceanographic cartographer Marie Tharp's discovery of the Mid-Atlantic Ridge, which supported the idea that continents move over time, was initially dismissed as 'girl talk.'

Scientists determined that tectonic plates moved the ocean floor by observing symmetric patterns of magnetic stripes on opposite sides of underwater volcano systems, which could only result from seafloor spreading.

Records of Earth's magnetic field on the seafloor validated plate tectonics

Matching glacial, fossil, and rock records, mountain ranges, and continental shapes across oceans was insufficient evidence for continental drift. Precise measurements of magnetic minerals on the ocean floor revealed seafloor spreading, which could only be explained by moving landmasses.

The theory of plate tectonics was not initially accepted until evidence became undeniable

Alfred Wegener proposed continental drift—the movement of large landmasses—in 1912 to explain why similar rock layers, plant and animal fossils, and glacial deposits were found on continents that were then unconnected. In the early 1960s, this was combined with evidence of seafloor spreading, mantle convection in Earth's interior, and earthquake and volcanic data outlining plate boundaries to produce the accepted theory.

The theory of plate tectonics first emerged from the theory of continental drift

German meteorologist Alfred Wegener proposed that the continents were all one giant landmass in the past, which he named Pangaea. Despite geological and climate evidence suggesting continental movement, his theory was dismissed until the 1960s.

Mid-ocean ridges are underwater volcano systems where tectonic plates diverge

New ocean crust is formed at these ridges as magma rises from Earth’s mantle and fills the space between the spreading plates. The speed of divergence influences ridge shape, with slow spreads forming rugged valleys and fast spreading creating smooth, wide slopes.

Scientists discover what looks like an underwater road

Crew aboard the Exploration Vessel Nautilus discvered a “yellow brick road” that looks it leads to Atlantis. Climage change may affect future ocean studies.

View maps of seafloor topography, earthquakes, and volcanic activity, which scientists use to create outlines of Earth's tectonic plates.

Continental drift is supported by matching evidence across disconnected continents

Mesosaurus fossils are found in South America and Africa, but these freshwater creatures could not have travelled across the ocean between continents. Rock layers in the Appalachian Mountains match those seen in Europe, indicating that the mountain belts were once connected.

Deep-sea trenches form when one tectonic plate subducts another underwater

Oceanic plates sink when colliding with less dense continental plates, bending the seafloor into steep depressions that can be almost 11 kilometers deep. Many of Earth’s strongest earthquakes occur at these plate boundaries, often featuring volcanic activity.

Slab pull and ridge push contribute to convection-driven oceanic crust movement

Through ridge push, after magma is projected up from the mantle, it cools and sinks, allowing gravity to help push older oceanic crust away. As this crust sinks into the mantle at deep-sea trenches, it pulls on the trailing crust behind it, accelerating ocean crust movement.

The art of 'undiscovering' phantom islands

Centuries of maps include islands and isles that appear to only exist on atlases. This article explores the discovery and "undiscovery" of such landscapes, which still persist despite modern technology. As recently as 2012, Google Maps showed an...

Most volcanic activity occurs in submarine volcanoes on the seafloor

At divergent plate boundaries in mid-ocean ridges, volcanic activity produces new ocean crust as the seafloor spreads. These areas are home to underwater mountains with extensive biodiversity due to redirecting ocean currents and concentrating food for marine life.

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.

Mapping the route options between the Pacific and Atlantic

This map shows some of the alternative trade route options that are available to shipping companies, from overland routes that rely on railways to transport goods coast-to-coast, to Arctic Ocean passages.

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.

Clark’s maps provided the first detailed record of the American West

Covering over 8,000 miles, William Clark’s maps charted rivers, mountains, and tribal territories with remarkable accuracy. Equipped with sextants, compasses, telescopes, and more, Clark became an expert at surveying—requiring extensive celestial and topographical observations each day.

No map of the Earth is perfect because each introduces inaccuracies in the shape, size, or orientation of landmasses and oceans by trying to flatten the planet's curved surface.

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

View a map of the world's major earthquakes from 1956 to 2022, which can be used to identify tectonic plate boundaries.

The missing continent that took 375 years to find

It took scientists 375 years to discover the eighth continent of the world, which had been hiding in plain sight all along. But mysteries still remain.

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.

Because seismic waves travel 100 times faster than tsunami waves—waves typically travel faster through solids than liquids—measurements of geological activity help tsunami detection systems provide early warnings.

Explore case studies of each type of convergent plate boundary

At these boundaries, a collision of two oceanic plates produces a curved chain of volcanic islands, like those seen in the Caribbean. A continental-continental plate collision results in plates buckling upward, forming large mountain ranges.

An interactive of the deep sea

Around 380 underwater cables power the Internet across the world.

On July 29, 1858, two steam-powered battleships met in the middle of the Atlantic Ocean. There, they connected two ends of a 4,000 kilometer (2,500 mile) long, 1.5 centimeter (0.6 inch) wide cable, linking for the first time the European and North American continents by telegraph.

Located in the Pacific Ocean, the Challenger Deep is the deepest point on Earth, extending to depths a mile deeper than Mount Everest is tall.

The history of the world map

What did people used to think the world looked like? From the beginning of human history to right before the age of exploration, learn how the world maps were created.

Watch footage from the moments the Titanic wreck was discovered by a joint US-French research team in 1985.

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

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

The Appalachian Mountains blocked east–west boat travel until the Erie Canal

The Appalachian Mountains, spanning from Alabama to Canada, long hindered inland commerce. The Erie Canal created the first reliable water route through the range by leveraging the natural valley of the Mohawk River, revolutionizing trade and migration.

Thunderquakes—seismic waves created when lightning strikes the ground—have enabled scientists to image underground environments near Earth's surface by detecting vibrations along subterranean fiber-optic cables.

Compare the true sizes of continents, countries, and other regions around the world by dragging them across a Mercator projection.

Explore coral reefs in Google's "street view"

Expanding its mission to map the world, Google Maps partnered with The Catlin Seaview Survey to introduce the first-ever underwater panoramas, making oceanic marvels like the Great Barrier Reef accessible to everyone. With Google Maps, the public...

View examples of rift valleys, the product of surface divergent boundaries

At these boundaries, tectonic plates move apart, stretching and thinning Earth’s crust as long valleys are formed from smaller, interconnected valleys and troughs. Ongoing rifting and erosion can further sink the valley, becoming a rift lake if volcanic activity becomes inactive.

Remnants of another planet that helped form the moon may be beneath Earth's surface

Large mantle structures beneath Africa and the Pacific Ocean may be the buried remains of Thea, a large Mars-sized planet that collided with Earth. The theory is supported by isotopic evidence from volcanic and lunar rocks.

Jefferson’s Lewis and Clark expedition joined the centuries-long hunt for Northwest Passage

For centuries, leaders pursued a direct seafaring trade route from Europe to Asia. Jefferson joined this quest by sending Lewis and Clark west, though they confirmed no such practical interior route existed across the continent.

A timelapse mapping more than 30,000 Transatlantic slave ship voyages

Roughly 12 million people from Africa were forcibly moved to North and South America over two centuries. This map meticulously showcases every ship's origin, destination, timeline, and more, revealing the scale of the Transatlantic slave trade.

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.

When oceanic plates sink beneath tectonic ones, they can generate magma

At converging oceanic-continental plate boundaries, the subduction of the oceanic plate introduces seawater that reduces the melting temperature of the overlying mantle. This causes it to melt into less dense magma, which can rise to fuel more volcanic activity.

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

The century of the Panama Canal

The Panama Canal connects the Atlantic and Pacific Oceans through a 51-mile route that transformed global shipping when it opened in 1914. This breakdown covers how it was built, the workers behind its construction, and why its future may be challenged by climate and competition.

View depictions of world maps throughout history

The first map to use latitude and longitude positions was created by Ptolemy in 150 CE, over 700 years after the oldest known world map, the Imago Mundi, was made with a Babylonian clay tablet. The Spanish crown created a secret master map from hundreds of sailors’ reports.

The San Andreas Fault is an example of tectonic plates sliding past each other

The transform boundary divides the opposing movements of the Pacific and North American tectonic plates, which create shear zones that distort and fracture rock. These movements produce shallow earthquakes as rocks are gradually displaced hundreds of miles.

The weather time machine

A fun interactive on how old ships’ logs are giving scientists new insights into the past and future of the Earth’s changing climate (w/maps and pictures).

Mapping the Tongan eruption impact

A team of scientists—with the help of an uncrewed boat remotely controlled from the UK—join forces to produce one of the clearest pictures to date of what took place underneath the water as an enormous volcano erupted near the Tongan mainland.

View a map of the distribution of mineral resources on the seafloor

Polymetallic nodules are found in regions near the middle of the Pacific Ocean, along the eastern coast of South America, and along the western coast of Africa, while cobalt-rich crusts span significant portions of the Pacific tropics east of the Philippines. Polymetallic sulfide deposits occur at tectonic plate boundaries, including areas within national jurisdictions.

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

Video and still images are combined with sonar data to create seafloor maps

Sonar works by sending thousands of sound pulses per second towards the seafloor, capturing the strength and timing of the returning echo. This data can accurately reveal depth, seafloor texture, and the presence of fish habitats to millimeter resolutions.

Travel through deep time with this interactive Earth

Explore key moments in Earth’s transformative history as continents drift and climate fluctuates over 4.6 billion years. The Smithsonian presents a series of interactive snapshots of the earth. From its toddler years during the Hadean period, when its surface was mostly molten, to the mostly unidentifiable landmasses of the future earth, 100 million years from now.