Science Behind the Explore Lincoln City Beachcombing Exploriance

The Science Behind Our Beachcombing Tours

Welcome! You’re on this page because you either attended an Explore Lincoln City Beachcombing Explorience, joined me one of our private tours, or you’re curious about how the Oregon Coast formed… and why agates are found here at all.

No matter how you arrived, you’re in the right place.

This page exists to share the science behind what we point out on the beach and to give you credible sources if you want to keep learning.

A quick note before we begin: science evolves. Geology is a relatively young science, and as we develop better tools for measuring time, movement, and chemistry, our understanding of Earth’s history becomes more accurate. What we teach reflects current best evidence, not fixed belief.

Beachcombing Looks Simple… But It Isn’t

Beachcombing looks simple.
You walk. You look down. You pick things up.

But what’s really happening is much bigger.

A beach is a dynamic geological system shaped by deep Earth processes and constant surface energy. Waves, tides, storms, and gravity are continuously moving, sorting, breaking, and redistributing rock that formed millions of years ago far from the shoreline. Coastal geomorphology and sedimentology study exactly these processes (U.S. Geological Survey; National Park Service).

Nothing you see on the beach arrived there by accident.

If You’ve Been on One of Our Exploriences

If you attended a free Explore Lincoln City Beachcombing Explorience, you may remember that we focused less on naming rocks and more on how they feel, little tells where to look and why.

This page gives you the long-form science behind those moments:

• why agates show up on this coast
• why some beaches are better than others
• why timing, tides, and storms matter
• and why many of these rocks began their story far inland

If you’re new here, this page explains what our tours are built on.
If you’ve already walked the beach with us, this connects the dots.

The Deep Origin Story: Siletzia and the Yellowstone Hotspot

The Oregon Coast Range is not made of typical continental rock.

Much of it is part of Siletzia, a massive large igneous province formed by enormous volcanic eruptions roughly 56–49 million years ago. Siletzia originated as oceanic basalt, likely formed above a powerful mantle plume and later accreted onto the edge of North America (Wells et al., 2014).

Current research strongly supports a link between Siletzia’s formation and an early phase of the Yellowstone hotspot, suggesting that this plume has been active far longer than Yellowstone National Park itself (Wells et al., 2014; USGS Yellowstone Hotspot).

This matters because it explains why the Pacific Northwest, including Oregon, is so rich in volcanic material.

Why That Matters for Agates

Agates, chalcedony, and jasper form when silica-rich fluids move through volcanic rock, filling gas bubbles, fractures, and voids. These silica deposits crystallize slowly over time, producing banded and translucent structures (USGS Volcanic Processes).

As volcanic terrains erode, these silica-rich materials are released. Over millions of years, rivers, landslides, and floods transported them westward. Eventually, many reached the Pacific Ocean, where wave action continued shaping and sorting them.

The beach is not where these rocks formed.
It is where their journey slows down.

Beaches Are Sorting Machines

Once rocks reach the coast, energy takes over.

Every wave carries force. That force moves material differently depending on hardness, density, size, and shape. Softer materials break down into sand. Lighter material moves farther. Harder, silica-rich rocks persist and gradually concentrate in specific zones (USGS Coastal Processes; Boggs, 2014).

This is why agates appear repeatedly in gravel lines, storm berms, and erosion zones.

Beachcombing success is not luck.
It’s observation plus timing.

Why Storms Change Everything

Storms dramatically increase wave energy. They can strip sand from beaches, exposing older deposits that may not have been visible for years. After storms, beaches often reveal:

• turned over gravel
• changes in sand deposition
• less-rounded material
• newly broken rock

This is why two walks on the same beach can produce completely different results (USGS Coastal Hazards).

Pattern Recognition Is the Core Skill

When geologists work in the field, they rely on pattern recognition, not guesses.

Color changes, banding, translucence, fracture patterns, and surface texture all provide clues about how a rock formed and where it came from. These skills are foundational in modern earth science education (National Science Teaching Association, Earth Science Literacy).

When someone says they have a “good eye,” they usually mean they’ve learned what to notice.

That’s what we teach first.

Why Certain Rocks Catch Your Eye

Rocks with strong contrast and internal structure stand out because the human visual system is especially sensitive to pattern and contrast. This helps us detect meaningful information in complex environments (Goldstein, 2014).

That moment when a rock “catches your attention” isn’t magic.
It’s perception working correctly.

Our tours help people trust that signal… and then confirm it using geology.

Context Matters More Than Naming

Names are useful. Context is powerful.

Understanding where a rock formed, how it moved, and why it ended up where it did tells a much richer story than a label alone. Modern geology emphasizes systems thinking because it builds real understanding rather than memorization (NSTA; NPS Interpretation Frameworks).

That philosophy shapes every Beachcombing Explorience or private tour we offer.

What Our Beachcombing Tours Are Built to Teach

Whether you joined a free Explore Lincoln City Beachcombing Explorience or a private tour, the goals are the same:

• Understand the volcanic origins of Oregon coast rocks
• Recognize how erosion and rivers moved material west
• Read beaches as energy systems
• Identify silica-based rocks by visible traits
• Interact responsibly with a living coastline

The goal is not to collect the most rocks.
The goal is to understand the story they tell.

Want to Go Deeper?

Curiosity is welcome here.
So is evidence.

You can download the scientific paper that informs much of this work here:

Geologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot
(Wells et al., 2014)

Below you’ll also find a curated playlist of videos that form the scientific backbone of our Beachcombing adventures.