This sweet simulation models geologic processes and features that are not easily observable, since they generally take place underground and over a long period of time.
The gelatin inside the cup represents the native country rock, the “geology” that happens to already be there. The sauce, pudding, or yogurt used represents the magma—molten rock, the source of igneous rock. The syringe represents a magma chamber, a large, hot, deep source of magma. Click to enlarge a diagram of volcanism below.
Volcanism (source: USGS)
Magma chambers can be located tens of kilometers underground. They exist near subduction zones, hot spots, rift valleys, and other areas of tectonic activity where the movement of tectonic plates can create fractures in the rock that create paths for magma to move upwards. In this Snack, as you force the “magma” to rise, it intrudes into the gelatin—the country rock. You might notice a big blob of sauce or pudding form. This is analogous to large bodies of magma known as plutons, which can be tens of kilometers wide. Multiple plutons that coalesce together are known as a batholith.
Sierra Nevada (source: NPS)
Plutons that remain underground and cool over long periods of time become intrusive igneous rock and can form the heart of large landmasses, and even mountain ranges. The Sierra Nevada Mountains in California (shown in the photo above) are an example of granitic plutons that formed underground about 100 million years ago and were exposed over time through erosion. The Sierra batholith forms the core of a mountain chain almost 650 kilometers long.
As your magma sauce forces its way through the gelatin, it can also create planar features, such as sills (intrusions that run parallel to country rock strata) and dikes (intrusions that cut across strata), as shown in the photos below.
Example of a dike (photo credit: Eric Muller)
Sometimes, a piece of gelatin will break off and can be seen embedded in the injected sauce. This is analagous to an inclusion of country rock suspended in cooled intrusive rock. These torn-off bits of rock are known as xenoliths.
When your magma sauce pierces the surface or erupts, it changes from intrusive to extrusive. Extrusive magma—that is, magma that has reached the surface—is called lava. Depending on its viscosity and quantity, lava can flow out smoothly or be ejected explosively, forming volcanic structures like those in Hawaii (made of basalt) or the Pacific Northwest (andesite and dacite), as shown in the photos below.
Hawaii (source: NPS)
Pacific Northwest (source: USGS)
As you eat your gelatin snack, you are effectively weathering and eroding your simulated rocks, removing surface layers and exposing the geologic formations beneath.