Crete is rising during earthquakes, and rivers are cutting down
May 24, 2025
Crete is a fascinating place—it is quite mountainous and, although it’s Greece’s largest island, its population is only about 650,000 people. We spent most of our time there hiking along the southwest coast (see previous post: https://landscapes-revealed.net/cretes-gorgeous-gorges/). The large gorges where we hiked are evidence that rivers have been cutting downward as a result of the land rising. This post focuses on historical earthquakes and evidence of uplift we saw along the southwest coast. I conclude with a brief geologic history—providing context for Crete’s current setting.
The great earthquake in 365 CE
On 21 July 365 CE, an earthquake on the southwest coast of Crete caused widespread destruction in Greece, Libya, Egypt, Cyprus, Sicily and Spain. On Crete, nearly all towns were destroyed. The earthquake was followed by a tsunami that devastated many coastal areas around the Mediterranean, killing thousands of people, destroying Alexandria in Egypt, and hurling ships 3 km (1.9 miles) inland.
There were no instruments to record the magnitude, but based on the extent of damage, geologists have estimated a magnitude of at least 8.0. The quake left a deep impression on people at that time and numerous writers referred to the event in their works. For example, the Roman historian Ammianus Marcellinus described the tsunami in detail, distinguishing three main phases—an initial earthquake, a sudden retreat of the sea, and an ensuing gigantic wave rolling inland. To read his account, click on the Wikipedia link in the Resources section below.
Evidence in the gorges
For location of sites mentioned below, please see my last post (link in first paragraph above).
Left-side photo: walking through Samaria Gorge. The steep, narrow walls indicate rapid incision of the river to cut this gorge. Right-side map: estimated amount of uplift (in meters) in western Crete during the 365 CE earthquake. Map is from Mare Nostrum News (link in references below).This view southward into Samaria Gorge shows how the river has cut down through the mountains.Jay is standing next to a fluvial terrace in Irini Gorge. This gravel layer was deposited in the river below us. Because the land is being uplifted, the river has cut downward to where it is now depositing its load. These older deposits are now above the river—an abandoned fluvial (i.e., river) terrace.
Evidence along the coast
Again, for locations, see my last post (link above).
At the bottom of Irini Gorge is the small town of Sougia. Notice that the beach is made of gravel. Walking east along this beach, we noticed gravel at an elevation of about 5 meters (16 feet)—see yellow arrow. The next photo provides a closeup.This is a closeup of the gravel pointed to in the photo above. The black arrow points to an unconformity between the limestone bedrock that is many millions of years old and the gravel that was at beach level before movement on faults uplifted it to this level during the 365 CE earthquake. Refer to the map above with estimated uplift amounts. Sougia is in the area that shows 4–5 meters (13–16 feet) of uplift.All around Sougia we saw this “bath-tub ring” indicating the level of the sea (red arrow) before faults lifted up the land in 365 CE. This photo was taken on the western edge of Sougia, at the start of the path to the ancient town of Lissos.This cove in Lissos, where we had lunch and a swim, also shows the “bath-tub ring” (red arrow). People by the cliff indicate the amount of uplift during the 365 earthquake was 4–5 meters.We next went to the coastal town of Loutro. The slopes are very steep and houses are built on the beach, so we did not see evidence of the 365 CE uplift. What we did see was a long-term record of uplift during earthquakes. Notice the house (right side of photo) on a flat surface that is probably a former beach that reached this level after multiple earthquakes. Higher up on the slope are more indentations that are probably even older beach surfaces that got elevated through many earthquakes over the years.When we hiked west from Loutro, we saw older beach surfaces more clearly (red arrows). The lowest one is probably from the 365 CE earthquake. The higher surfaces are older beaches that reached these levels after being uplifted during many earthquakes. Geologists call these surfaces marine terraces, because they form in the surf zone of oceans and are then uplifted to successively higher elevations over time. To see more about how marine terraces form, see my post about Point Reyes National Seashore in California: https://landscapes-revealed.net/the-geology-of-point-reyes-national-seashore/.
Brief geologic history
Although they are both located in the eastern Mediterranean Sea, the geology of Crete and Cyprus are very different (for Cyprus, see my posts on 23, 27 April and 4, 12 May). Like Cyprus, Crete is caught in the collision zone between the African and Eurasian plates. Both islands are located north of subduction zones, where the oceanic part of the African plate is being subducted beneath the Eurasian plate. Both islands also contain abundant limestone rocks that formed in the Tethys Sea and were then uplifted onto land during the collision process.
This tectonic map shows the location of Crete at the southern end of the Aegean Sea and north of the Hellenic Arc (subduction zone). Elevation (green to red colors) and ocean depths (blue to magenta colors) are in meters (1 meter=3.28 feet). As described in my first post about Cyprus—https://landscapes-revealed.net/cyprus-a-pop-up-island-between-converging-plates—the Arabian plate has already collided with Eurasia, creating a space problem that is pushing the Anatolian plate westward. This westward extrusion of the Anatolia plate (i.e., Turkey) is causing the Aegean Sea to extend. The Aegean is underlain by continental crust, but it has been thinned by north–south stretching. Twenty million years ago, the Hellenic Arc was a straight east–west line. Since then, the arc and the island of Crete have moved southward because of the north–south extension. Figure from Rahl et al., 2004 (reference below).This south–north profile shows Crete’s location north of the Hellenic arc (subduction zone). The African plate (left side—to the south) is being subducted beneath the Eurasian plate (right side—to the north). Islands north of Crete are the volcanoes being produced by subduction-induced melting. The volcano shown erupting is Santorini, where we traveled after leaving Crete. Figure is from “Geology: how was Crete created?” (see references below).
This image is the subduction zone that was active in California at the latitude of San Francisco about 100 million years ago. As in Crete, oceanic crust was being subducted beneath the continent and forming volcanoes generated by mantle melting. The Franciscan Complex—named after San Francisco—is an accretionary complex formed as an assemblage of pieces scraped off the down-going oceanic plate and accreted onto the overlying continental plate. The scraped-off pieces are parts of upper mantle (e.g., serpentine), oceanic crust (e.g., pillow lava), und overlying marine sediments (e.g., chert and limestone). Pieces are separated by thrust faults—the black lines in the Francisco Complex (blue on the image).
About 20 million years ago, Crete would have looked like the image above. Starting about 15 million years ago, the continental crust above the subduction zone began to stretch, causing the accretionary complex to be uplifted and exposed on land.
This geology map of Crete shows the rock types. All of the rocks on Crete, except Neogene sediments and Alluvium, were formed somewhere else. Like the Franciscan accretionary complex (above figure), the rocks were part of the oceanic (African) plate that were carried to the continent and “scraped off” onto the overlying continental plate during subduction. These packages of rocks are separated by thrust faults, as shown in the Franciscan Complex above. Figure from Rahl et al., 2004 (reference below).
Back to the 365 CE earthquake and volcanoes
It’s a little confusing but Crete is undergoing both compression and extension. There is compression because the African and Eurasian plates continue to collide via the Hellenic Arc subduction zone. At the same time, the upper continental plate (Aegean Sea) is extending because of a variety of factors that are still being debated.
The 365 CE earthquake is interpreted as movement on a normal fault caused by extensional processes along the southwest coast of Crete. Large magnitude 8+ earthquakes are rare in extensional environments, but apparently they occur in Crete.
This figure illustrates a normal fault that is probably similar to the faults that are uplifting the island of Crete. Imagine that the down-dropped (hanging wall) side of the fault is under the ocean, and the uplifted (foot wall) side of the fault is the mountainous region in southwest Crete. With each earthquake, the mountains are lifted higher and the former beaches are lifted higher too. These former beaches are the flat terraced surfaces visible on the south-facing mountain slope.
The final part of our trip was to Santorini, a volcanic island that another part of the Hellenic arc system. My next post—about Santorini—will be posted in a few weeks.
