Volcanism and Erosion

Volcanism

The Mossfell islands are driven by the Frisland hotspot and are between approximately 22.1 million and 900,000 years of age. The archipelago stretches from the jagged coasts of Mossfellheim to the well eroded beaches of the Lonely Bob seamount. The chain's movement is fueled by the migration of the North American Plate over the Mossfell hotspot. Unlike most island chains, the Mossfells did not develop in a perfect volcanic "line" but instead are a delineated chain (Lonely Bob to Mossfellheim) with two additional axes - one which stretches north from the Isle of Hens to Gasmensyi and another cryptic line consists of the Warwick Reef and Whalebone Reef.

Mossfellheim consists of a single active shield volcano and is the youngest island. It is highly active, with the last eruption occurring July 2015. The largest island of Neffannafjall consists of five coalesced shield volcanos arranged in a ring - giving the impression of an immense false caldera. There is evidence to suggest that the last time these volcanos erupted was only 2,000 years ago, indicating that these calderas may still be active. The oldest islands in the archipelago, Lonely Bob and Nishsystir, are the well eroded peaks of the oldest shield volcanos of the chain. Due to the archipelagos' steady volcanism, the islands are also noted for their daunting heights. The peak of Mossfellheim stands at 7,659 feet (2334.5 meters). The tallest peak of the Neffannafjall, Sjodjanji Tar, stands at 7,221 feet (2201 meters).

The islands today demonstrate many volcanic characteristics. On the younger islands of Neffannafjall and Mossfellheim, it is easy to find the remains of pahoehoe and a'a' flows. Pumice stones and lava bombs are common features on beaches across the chain. On the older islands of St. James and St. Anne, many lava tubes pock the hillsides and have served as unique microenvironments for cave-dwelling organisms.

Erosion

Throughout their existence, the Mossfell islands have undergone a considerable amount of erosion. Being on the cross roads of the Labrador current to the north and the Gulf Stream to the south, many of the islands have undergone drastic reductions in size due to weathering from wind, water, and organisms. Once their volcanisms began to subside, the forces of wind, rain, and snow slowly broke down surface lava flows into fine sand. Due to their northerly position, snow and ice have had a particularly strong effect on the erosion of these islands compared to other island chains, and is likely partly responsible for the rapid erosion of the older islands. This initial erosion produces a soil poorly suited for most plants, but great for pioneer species such as lichens and mosses. As these pioneer species grew and died, their remains became richer and thicker soil, enabling the land's colonization by larger and more complex plant species. Eventually the cycle repeated to the point where a thick layer of topsoil was created and the lava flows were transformed into a thriving ecosystem teeming with forests and grasslands.

As an example, the islands of St. James, St. Anne, and Isle of Hens are known as the "Bountiful Isles". These islands are characterized by their moderate elevation, lush soils, and pleasant climate. The soils on these islands are particularly rich due to both the minerals from ancient eruptions and the long period of erosion. As a result, these islands were the first to be colonized by the Norse, Narragansett, and later European colonists. The initial steps into this pattern of succession can be seen on the slopes of Mossfellheim where ghost ferns have colonized a nearly inhospitable wasteland after lichens broke up the volcanic flows. Within a few million years, the decomposing remains of the ghost ferns will produce a rich soil for a new wave of trees and grasses to colonize. 

It is important to note that in an island chain erosion can provide substrate for life, but only so much erosion can occur before losing the entire island. Evidence from the oldest seamount, known as Lonely Bob, indicates that it likely rose above Atlantic Ocean 22.1 million years ago during the Burdigalian timescale of the Miocene. Lonely Bob at one time had a size comparable to the modern-day Mossfellheim. It is now an incredibly eroded archipelago whose shallow waters occasionally proved hazardous to ships. 

Sinking beneath the waves is not the end for the submerged islands. The final stage for these volcanic remnants is to become low-lying lagoons and atolls. Before the island starts its decline, coral reefs may begin to encircle it. As the island subsides, coral reefs fully encircle the doomed island and eventually once the island fully erodes all that is left is reefs and lagoons. These reefs will outlive the volcanic islands, and are still a location full of bountiful life.