Outcrop

Point your camera at the landscape around you to learn about its geology: what the rocks are, when and how they formed, and where the continents were at the time. It also works offline.

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Free, for iPhone and Android. Geologic maps worldwide from Macrostrat.

Earth’s history

See where each rock fits in Earth’s 4.5-billion-year history.

Cenozoic 66–0 Ma
Mesozoic 252–66 Ma
Paleozoic 539–252 Ma
Precambrian 4540–539 Ma

Hover over or tap the timeline to see periods and events.

Geologic maps in augmented reality

Hold your phone up to a canyon wall, a road cut or a distant ridge, and Outcrop draws the geologic map over the landscape. It names the rock in the center of the screen and labels nearby peaks and lakes.

The camera view of a river, with the geologic map drawn over the far bank. The Platteville and Glenwood Formations are shown in green, and the rock in the center of the screen, 480 meters away, is identified as Late Ordovician in age.

See where it formed.

See the globe as it looked when a rock formed, as far back as 1.8 billion years ago. Back to 540 million years ago the maps are Christopher Scotese’s PALEOMAP maps, and before that they are maps we drew in his style. Outcrop shows where the rock was then, how far it has moved and how fast. Press play to watch plate tectonics carry it to where it is today.

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The globe 450 million years ago, in the Ordovician. The rocks of the Platteville and Glenwood Formations formed 17 degrees south of the equator, in the tropics, 7,620 kilometers from where they are now. They have moved an average of 4.5 centimeters a year.

Glacial history

Watch the ice sheets grow and melt through the last ice age. See how thick the ice was at any spot, and whether a mountain glacier reached it or a glacial lake covered it.

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The globe about 20,100 years ago, with ice covering most of Canada and the northern United States and glacial lakes along its edge. Minneapolis lies under 970 meters of ice, and sea level stands 106 meters lower than today.

Know what’s under your feet.

Outcrop opens to the rock you’re standing on, with its name, its age, what it’s made of and how it formed.

The geologic map tilted over Upheaval Dome in Canyonlands, with the ring of Navajo Sandstone around it outlined. Below the map are the Navajo Sandstone's details: Early Jurassic, its rock types, the map's description, and its age of 201 to 175 million years on a timeline of Earth's history.

See how it formed.

See the setting a rock formed in, from desert dunes to the deep sea floor, and what to look for in the rock. A photo shows the same kind of setting today.

How the Navajo Sandstone formed: a cross-section of eolian dunes with the dunes highlighted between an interdune flat and loess. Sand was blown up the dunes' gentle backs and avalanched down their steep faces; look for cross-bed sets, often meters thick, of well-sorted, rounded sand grains. Below, a photo of the Great Sand Dunes in Colorado as a modern analogue.

See the layers below.

Where Macrostrat has a stratigraphic column for the area, you can see the layers beneath you from the surface down, with each layer’s age and the fossils found in it, and the gaps in the record.

The rock column under the Navajo Sandstone in the Paradox Basin: 47 units spanning 1.9 billion years, from the Navajo at the surface down through the Permian and Pennsylvanian to a gneiss complex 2 billion years old, with 893 million years missing below the Cambrian.

Search for rocks.

Search for a rock type, an age, a named unit or a fault. Outcrop highlights matching places on the map and tells you how far away the nearest one is, even if it’s off screen.

A search for iron formation over Saint Paul, Minnesota. The nearest match is 150 kilometers west, on the Cuyuna Range.

From bedrock to topsoil.

Bedrock and faults come from Macrostrat’s geologic maps, which are more detailed in some places than others. Switch to Quaternary geology to see glacial and river deposits and recently active faults, or to Soils to see the soil and the plants that grow in it. All three layers work on the map and in the camera view.

Bedrock and faults worldwide
Quaternary, active faults and soil in the US

The layer picker over the geologic map of the Grand Canyon by the Bright Angel Fault: a satellite or map base, Bedrock from Macrostrat, Quaternary from the USGS and Soils from the USDA NRCS to choose from, and Saved areas below.

Save it before you go.

Outline an area to download it to your phone, and the map and camera view will work without a signal. Fossil records and active faults in the camera view still need a connection.

Saving the Grand Canyon for offline use: the save at 75 percent, six of its eight steps along, with satellite imagery switched on.