Editor’s note: what a cool way to see Portugal’s famous Algarve region! For more of Morgan’s geology-based adventures, be sure to click here to visit her index page.

Lagos’ famous rock formations are riddled with fossils, making the town a perfect destination for geology enthusiasts and tourists alike. Since Portugal allows the collecting of fossils (or at least lacks any legislation preventing it at this time), you may even be able to take a few small choice specimens home as mementos of your journey.

My own self-guided Lagos adventure took me to a deserted sea cave, accessible only after a strenuous hike. Inside this quiet refuge, I discovered extraordinary fossilized mollusks that were not only perfectly preserved, but also fully crystallized, transforming into stunning natural specimens.

Clear waters of Lagos

Journey Down a Spectacular Coastal Formation

Nestled in Portugal’s popular Algarve region, Lagos is a popular seaside destination for European tourists as well as those from other locations. While many seek the busy nightlife and fantastic food, the stunning rock formations and beaches have their own draw. Over millions of years, the pounding of waves and erosion have sculpted these geological features, including imposing cliffs, towering sea stacks, and networks of hidden caves.

Lagos sea tower at night

One of the most famous of those formations is the Ponte da Piedade, located at the southern tip of the Lagos region. Its striking sea pillars and caves are equally impressive when viewed either from the cliffs above or at sea level. Thankfully, a well-defined path allows for an easy 30-minute walk from central Lagos.

Top of the hike

Near this area, I surveyed the steep rocky cliffs for pathways down to the Atlantic. Since every avenue seemed precarious at best, I chose somewhat randomly – and felt relieved to be wearing proper footwear after spotting abandoned flip flops and sandals embedded along the way.

As I grabbed ahold of easily-crumbled cliff wall partway down the climb, I immediately noticed that my hand sat directly on a clam-like fossil – a great indicator of what treasure might lay below. Finally reaching the water, I found my effort rewarded with a completely empty beach, caves beckoning from either side.

Halfway down the cliff

While strolling along the shoreline itself, I noted that almost every item that seemed
to be a beach rock was actually a fossil. Fossilized shells typically litter the ground on Lagos beaches. Many of the cliff walls and caves are essentially made of fossils, too,
so as you hike or swim through passages, be sure to keep an eye out for fossils embedded in the limestone walls.

Wall filled with fossils

Wandering into the cave on my right with waves crashing all around felt like strolling
through a portal to another world: a sea cave without a ceiling, allowing beams of light to shine onto a pile of sparkling, perfectly preserved fossils. Their corkscrew shapes reminded me of pasta, but the most striking part was certainly the crystals that made up part of the specimens. These lovely but easily-crumbled crystals seem to even contain portions of the original mollusk’s body.

Inside a Lagos cave

After a few hours of joyful exploration, I made the treacherous reverse hike out, a small prize in hand. Unsure of the classification of the gorgeous crystallized mollusks at the time, I took photographs of these spiral-shaped, sparkly fossils to a geology museum in Lisbon (a mere three-hour bus ride away).

My prize

Continuing Research in Lisbon’s Museu Geológico

This museum, despite its unremarkable and easily-missed exterior, is a worthy stop for geology enthusiasts. It houses thousands of specimens, ranging from massive ammonites to intimidating dinosaur leg bones, including the Lourinhasaurus, which was first discovered in Portugal. The museum is wide-ranging enough to even include early human tools. What’s more, the museum provides written guides in multiple languages, including English.

Laurinhasaurus leg bone

Inside the Museu Geológico I was able to compare the specimens I’d found in the Lagos cave to the museum’s detailed displays. This allowed me to identify the crystallized mollusks as Turritella, learning how the crystalline structure had been created as a result of the minerals that slowly leached into the shell as it fossilized.

The display case that matched my fossil

The museum also provided an opportunity to dig into the longer timescale of how these fossils came to exist in the area.

Lagos’ Geological Origins

During the Late Cretaceous period, the Iberian Peninsula was submerged beneath a shallow sea. During this time, Lagos was of course not the heritage-rich Portuguese city we see today, but rather the sea floor itself. Over millions of years, sediments from the shells and skeletons of the animals in that sea settled on the ocean’s floor, gradually piling up on each other and compacting to form limestone deposits.

Over the next several million years, the Earth’s plate tectonics continued to shape the planet’s crust. The Iberian Peninsula (which includes current-day Portugal and Spain) began to rise, gradually emerging from the depths of the sea. This geological activity exposed the ancient seafloor sediments that now make up much of Lagos’ landscape.

Most recently, the elements (winds, storms, and powerful waves) wore down much of that limestone into the striking columns, caves, and sand we experience on the beaches of Lagos now. Because the Lagos area was originally a seafloor, all of those contain a multitude of easily-found fossils. These ancient creatures can now be literally stumbled upon as you take a stroll down the beach – which is itself made of sand also composed of their preserved bodies.

Lagos beach at night

Overall, Lagos offers not only a breathtaking coastal experience, but also a worthy geological experience. Its origins in a submerged ocean floor, the sculpting forces of nature, and the abundance of fossils all contribute to its unique draw. Whether you’re a casual visitor looking for a good meal and a single fossil to take home or a dedicated geology enthusiast looking to learn, Lagos has something to offer. And if you’re venturing onward, the Museu Geológico in Lisbon adds another layer of depth to your exploration.

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