Layers of minerals revealed by erosion give Vinicunca its distinct colorations

Inca trail interactive map

Machu Picchu gets all the attention, but it’s definitely not the only Inca ruin in the area. Some dedicated trekkers opt to see the sites through a multi-day hike down the Inca Trail, which spans 26 miles from the Sacred Valley to Machu Picchu and reaches elevations as high as 13,800 feet above sea level. This 3D tour gives a sneak-preview of the ruins along the route, and the intense topography.

How did the Inca build Machu Picchu?

How did the Inca, a people without iron or steel, build a city that has withstood hundreds of years of earthquakes and inclement weather? Machu Picchu stands atop steep landslide prone slopes and active fault lines and gets up to 80 inches of rain...

What is the rarest color in nature?

Plants, animals, or minerals found in nature bear almost every color imaginable. There are two factors that influence what hues you see in the wild: physics and evolution. So, which colors are you least likely to see in the natural world? Victoria Hwang explores one of nature's rarest spectacles.

Cerulean eruptions result from sulfur being heated by molten rock

During eruptions, warm-colored lava at temperatures between 700 and 1,200 degrees Celsius (1,300 and 2,200 degrees Fahrenheit) burns minerals as they escape from underground reservoirs. In some volcanoes, such as Indonesia's Kawah Ijen and Ethiopia's Danakil Depression, abundant sulfur compounds that burn with blue flames appear to change the color of the melted rock.

A virtual reality experience of Machu Picchu

If you can’t make it to the Andes, this virtual-reality experience—created using 360-degree cameras, and 3D modeling and sound design—is the next best thing. It lets you explore all the site’s major landmarks, including the Sun Temple and the Temple of the Condor, while listening to the sound of the wind whipping through the ruins, birdsong, and audio commentaries from expert guides.

Machu Picchu is an ancient Incan citadel set high in the Andes Mountains in Peru, abandoned for centuries before its rediscovery in 1911.

Machu Picchu, 101

Machu Picchu was built right on top of two intersecting fault lines, which makes it even more baffling how its temples and terraces have survived for more than 500 years—especially since no mortar was used to hold the precisely cut stones together. As this three-minute NatGeo video explains, this ingenious construction method allows the stones to bounce in place when earthquakes hit, shaking and rattling but rarely collapsing.

Meet Pachacuti, the king who built Machu Picchu

In the 1400s, King Pachacuti of the Inca Empire wanted a summer resort for himself, his family, and his entourage. So he and his builders set out to build Machu Picchu, a feat of engineering, carving, construction, and more. Its 700 terraces remain intact today, while its trapezoidal stones inspire construction efforts around the world. Learn about the fascinating process of building this wonder of the world here.

The conditions needed for cloud iridescence, or rainbow clouds

The relatively rare phenomenon occurs when sunlight scatters off tiny water droplets or ice crystals in thin, newly-forming or semi-transparent clouds, such as altocumulus, cirrocumulus, lenticular, and cirrus varieties. This effect is similar to what is seen in soap bubbles and mother-of-pearl shells and produces pastel-like colors.

The last Inca grass suspension bridge in Peru

High in the Peruvian Andes, the aging Q’eswachaka bridge sags precariously over the Apurímac River. It has been built and rebuilt continuously for five centuries. Read more about it here.

Scientists are still confused how Machu Picchu was built

Machu Picchu, the 15th-century Inca city high in the Andes, continues to fascinate experts with its mysteries. The methods used to transport and carve its massive stones—some weighing 15 tons—remain unclear. Theories range from hundreds of men dragging the stones to innovative techniques like using expanding wet wooden wedges for precision carving.

Sacsayhuaman, the Inca's largest structure

Less well-known but arguably more impressive than Machu Picchu is Sacsayhuamán, a 15th-century fortress-temple on the outskirts of Cusco. The site also features huge stones—some weighing more than 100 tons—carved into interlocking blocks and joined together through mortarless masonry. Archaeologists estimate it must’ve taken some 20,000 laborers to complete construction. This video offers a clickable 3D virtual-reality tour of the site.

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.

Niagara Falls flows over 400-million-year-old layered rock

The falls cut through distinct layers of ancient rock: a hard cap of Lockport Dolomite sits atop softer layers of Rochester and Queenston Shale. This structure allows the falls to maintain a steep vertical drop as erosion undercuts the caprock.

Volcanic activity can lead to the formation of fertile soils

Ejected rock can introduce key minerals found in fertilizers, including iron, magnesium, and potassium, to improve soil quality. Ash and basalt crystals can be easily absorbed into soils, infusing them with sulfur, oxygen, chlorine, phosphorus, calcium, and other critical elements.

Lava flow viscosity plays a significant role in the type of volcano formed

Thin, runny flows spread quickly before cooling, producing expansive layers that build over time into wide shield volcanoes. The ejection and fast hardening of thicker lava flows and pyroclastic material create steep slopes and the characteristic cone shape of composite volcanoes.

The mysterious qualities of obsidian and magnetite

Obsidian is a dark volcanic glass created when lava cools quickly and frequently contains magnetite, a key early mineral used in compasses. Large deposits were discovered and used in central Mexico by the Toltecs roughly 1,000 years ago at the ancient site of Teotihuacan. This essay explores obsidian's cultural impact and the mysterious presence of magnetite in migratory birds.

The Valley of Mexico sits over 7,000 feet above sea level

Once dominated by the shallow waters of Lake Texcoco, the high-altitude Valley of Mexico—surrounded by volcanic peaks—was home to the Aztec capital Tenochtitlan. This resource breaks down the region’s unique geography and why it became a cradle of Mesoamerican civilization.

Often considered the largest natural mirror on Earth, Bolivia's Salar de Uyuni is the world's largest salt flat—a desert formation covered in minerals.

The centuries-old history of titanium white goes back to the Inca

Titanium white can be found in items ranging from paint to pills. Though it was created in New York in 1908, the pigment was first used hundreds of years earlier by the Inca, according to this article.

View a gallery of diagrams for each volcano type with glossaries

The three major types of volcanoes—cinder cone, composite, and shield—each exhibit unique, lesser-known subterranean and surface features, including lava bombs, lahars, and spatter. Other types of volcanoes include lava domes, calderas, fissure volcanoes, and Maars and tuff rings.

Ceren: The Maya Pompeii (sans all the bodies)

The Maya village of Ceren in El Salvador was preserved by volcanic ash from 1,400 years ago, revealing insights into ancient Maya commoners' lives. Ceren villagers had autonomy in their daily activities, and excavations reveal evidence of communal decision-making and event hints at the presence of a community sauna. Dive into more of the archaeological finds on how businesses were run, how they prepared for disaster, and more.

Speleothems are diverse mineral formations that form in air-filled caves

Speleothems like stalactites and stalagmites form when water deposits minerals after a cave rises above the water table and fills with air. These formations preserve the mineral deposits, which may serve as climate proxies, for as long as a million years.

Mapping tourism at Machu Picchu

Only 750 people lived at Machu Picchu at its height, but today, almost ten times that number trample through its delicate plazas and agricultural terraces every day. This data visualization vividly illustrates the skyrocketing numbers of visitors to Machu Picchu over the decades, and highlights the risks of over tourism, including soil erosion and other environmental threats, and negative social and economic impacts.

From the surface, Mars can appear butterscotch, golden brown, and even green

Images from orbiters, landers, and rovers show that Mars has a mix of surface colors resulting from variations in the mineral compositions of different regions. The reddish tint when viewed from Earth comes from kicked up particles of rusted iron.

Water is naturally tinted with a slight blue, but sediments and organics can alter its color

The innate coloration comes from water absorbing red light in the visible spectrum more than green or blue, giving shallow waters in some parts of the Caribbean their turquoise hue. If sand is light, it can be churned up by turbulent water, clouding its appearance. Plankton and other organisms can color water by affecting how the rest of the spectrum is absorbed or reflected.

As of 2026, the rarest mineral on Earth may be kyawthuite, an orange gemstone whose only known specimen was found in Myanmar in 2010.

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.

Machu Picchu before it was a tourist attraction

The Machu Picchu we know today is familiar thanks to its neatly manicured plazas, lovingly preserved stone buildings, and ever-present hordes of tourists. But that’s not what Hiram Bingham saw when Melchor Arteaga led him to the site in 1911. Back then, it lay covered by centuries of tropical overgrowth.

Yale returns Inca artifacts to Peru

From the time he came upon Machu Picchu in 1911, Hiram Bingham began removing artifacts and human remains from the site and bringing them back to Yale University. Yale's Peabody Museum held them for 100 years, despite demands by the Peruvian government and the public that they be repatriated. Finally, in 2011, Yale returned thousands of items, including ceramics, jewelry and human skeletons.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

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.

Is the Inca maiden the world's best-preserved mummy?

Found atop a snowy peak in the Andes, this teen mummy is at least 500 years old. Watch this four-minute video to see the Inca maiden, a mummy so well-preserved that small details, such as her many braids, are clearly defined.

See Mount Vesuvius from space

Mount Vesuvius is one of the few active volcanos on Europe's mainland. See it from space in this photo from NASA's Earth Observatory. This natural-color image was taken on January 2, 2022, during a break in cloud coverage.

Geological features on Mars' surface provide evidence of massive past flooding

The presence of river valleys, enormous canyons, and other structures carved by water on Earth suggests that water flowed abundantly across Mars' surface. The layering of rocks in the walls of these structures indicates the intensity and volume of these flows.

The US senator who found a city in the sky

Dr. Hiram Bingham, a Yale graduate and explorer, is credited with rediscovering Machu Picchu in 1911. Financially supported by his marriage to the Tiffany jewelry heiress, Bingham ventured into the Peruvian Andes in search of the lost Inca city of Vilcabamba. Instead, guided by local farmer Melchor Arteaga, he stumbled upon the awe-inspiring ruins of Machu Picchu.

The unsolved mysteries of Machu Picchu

Who lived there? How did they get all that granite up there? Who were the 100 bodies found buried here, and why did some of them have elongated heads? Explore eight of Machu Picchu’s unanswered questions while scrolling through panoramic, clickable street-view images of the site, in this guide from Google Arts and Culture.

Ancient sunken plates may influence mantle convection and surface motion

Research suggests sunken tectonic plates can collide, assemble, and break apart to form structures called large low-velocity provinces. LLVPs can significantly enrich rising magma plumes with elements commonly seen on Earth’s surface.

What llama beans can tell us about the Inca Empire

Fun fact: Llama bean is just another term for llama poop. Another fun fact: Scientists are using these beans and related microorganisms to learn more about the Inca Empire. Read this article to learn how.

Rediscovering the Inca Empire

In 1991, anthropologist Johan Reinhard was trekking up the snowy face of a dormant volcano when he came face to face with the mummified remains of a teenager who had been sacrificed to the Incan gods centuries earlier. The story of “Juanita the Ice Maiden” is just one of the riveting tales featured in this four-part series from the popular podcast "History Hit".

Critical mineral production may lift impoverished regions out of poverty

Mineral wealth can provide public revenue and economic livelihoods to those in mining regions. However, poor management and lack of oversight can cause human rights abuses, environmental degradation, and significant greenhouse gas emissions.

Cooling lava naturally creates hexagonal cracks to evenly relieve stress

When lava cools and turns into rock, it contracts and builds up tension, particularly when held in place by the surrounding landscape. Just as drying mud cracks, initial cracks in the rock are random, but quickly organize into a hexagonal pattern, which scientists consider the most space-efficient shape.

Human sacrifice in the Inca Empire

In the lands ruled by the Incas, mountain deities were well-respected and related summits were often selected as places for making the most important of all offerings — human sacrifices.

Photos and descriptions of unique plants found in the Amazon rainforest

It’s the plants that provide homes for the incredible diversity of Amazon animals. Read about 29 of the most fascinating Amazon rainforest plants.

Weird ways critical minerals are being mined

Critical minerals like lithium, cobalt, and graphite are economically crucial non-fuel resources subject to supply chain risks. To diversify production, scientists developed odd ways to harvest them. This article breaks down the weirdest approaches, including extracting minerals from seawater using algae, phytomining plants, and asteroids.

A 37.41 carat, bicolor diamond likely formed from two distinct geological processes

Discovered in a Botswana mine, half the stone is clear, having formed from carbon being squeezed under extreme heat and pressure into a tight crystal structure. The pink half formed earlier and resulted from minor bending of the crystal during tectonic activity without causing it to brown or break.

A diamond's color comes from impurities, defects, and unique formation processes

While most diamonds are transparent and sparkly, the presence of nitrogen and boron during formation can make them yellow, orange, or blue. Radiation can produce green diamonds, and structural deformities can introduce red hues.

With a height three times that of Mount Everest and an area roughly the size of Poland, the Martian shield volcano Olympus Mons is the largest volcano in the solar system.

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.

What was the Great Inca Road?

In little more than 100 years, it grew from a small kingdom in the highlands of Peru to become the largest empire in the Americas. Read about the critical role played by the Great Inca Road.