The Pacific Northwest is home to some truly fascinating geology. From the coast to the mountains to the high desert, the region’s rocks and landscapes tell amazing stories about the Earth’s deep past.

Did you know that rocks are changing all the time? Even though they look like they’re always the same, they’re actually transforming very slowly, over millions of years, through a process called the rock cycle.

 Let’s explore the rock cycle and see how it works.

It all starts with the three types of rocks that make up planet Earth: igneous, sedimentary, and metamorphic. Igneous rocks form when magma—the hot liquid rock that flows underneath Earth’s surface—cools and hardens. Basalt, granite, and obsidian are all igneous rocks. Over time, weathering and erosion from wind and rain causes igneous rock to break down into tiny pieces like sand or gravel. When these tiny pieces are packed tightly together over millions of years, they become sedimentary rock. Sandstone and limestone are two examples. As more time passes, these rocks sink deeper into the ground, where intense pressure and heat can transform them into a denser type of rock known as metamorphic. When limestone undergoes metamorphosis, for example, it becomes a much denser rock called marble.

Metamorphic rocks can work their way back to the surface through the process of uplift, or they can melt and join the magma flow underground. The magma can then slowly cool and harden, working its way up to the surface again as igneous rock, or if pressure keeps building, it might stay in its molten state until it erupts from a volcano!

Whether it’s by slow, steady cooling or sudden eruption, once magma makes its way to Earth’s surface, the rock cycle begins all over again.

Explore From Home

Geologists study the formation and movement of rocks, minerals, fossils, and landforms to better understand our planet’s deep history. Head to the Museum of Natural and Cultural History’s website and try being a geologist for a day! The museum’s new Rocks and Lava webpage is full of geology-focused games, videos, and rockin’ hands-on activities you can do from home—and it’s available in both Spanish and English. Find it—along with lots of other family-friendly museum fun—at mnch.uoregon.edu/explorefromhome.

The Museum of Natural and Cultural History is open to the public Wednesday through Sunday 11:00 a.m. to 12:00 noon for seniors and COVID-vulnerable visitors, and 12:00 noon to 3:00 p.m. for everyone. Stay tuned to our website (mnch.uoregon.edu) and follow us on social media for the latest on our fall lineup of virtual events.