An experience like no other! Experience a drive across the ocean floor! Check before you go - https://www.ministersisland.net/tide-schedule.htm. The tombolo is only accessible at certain times of the day.

PLEASE DRIVE WITH CARE: If travelling to Ministers Island by vehicle, it is recommended to drive on the gravelly portions of the bar at low speeds. Sandy areas can be quite deep and vehicles may get stuck.

Saint Andrews is a town in Charlotte County, New Brunswick, Canada. It is at the southern tip of a peninsula, extending into Passamaquoddy Bay. Several hundred metres offshore immediately northeast of the town stands a geographical novelty, a 500-acre Maritime tidal island that it is accessible at low tide by a wide gravel bar suitable for vehicular travel. For many thousands of years Ministers Island (Consquamcook) was the seasonal home of the Peskotomuhkati indigenous people. A tidal island is a piece of land that is connected to the mainland by a natural or man-made causeway that is exposed at low tide and submerged at high tide. Tidal islands are common in many parts of the world. These causeways connecting the island with the mainland allow visitors to reach the island by land but require them to wary of high tides. The causeway connecting Ministers Island to Saint Andrews is actaully a naturally occuring landform known as a tombolo.

What is a Tombolo?

A tombolo is a sandy isthmus. A tombolo, from the Italian tombolo, meaning 'pillow' or 'cushion', and sometimes translated as ayre, is a deposition landform by which an island becomes attached to the mainland by a narrow piece of land  - a thin sand bar or spit. Tombolos are also sometimes referred to as “tied islands”, because it seems to tethered to the coast. 

How a Tombolo is Formed - Wave Diffraction and Refraction

A true tombolo is formed by wave diffraction and refraction. Longshore drift occurs as waves push sediment (which may consist of sand, silt, and clay) towards the coastline at an angle. Instead of landing on the beach, this sediment begins to build up between the beach and an island, creating the bar mentioned above and effectively “tying” the island to the mainland. As waves near an island, they are slowed by the shallow water surrounding it. These waves then bend around the island to the opposite side as they approach.  As the water moves more slowly around the island, it picks up sediment along the way. The wave pattern created by this water movement causes a convergence of longshore drift on the opposite side of the island. The beach sediments that are moving by lateral transport on the lee side of the island will accumulate there, conforming to the shape of the wave pattern. In other words, the waves sweep sediment together from both sides. When the waves meet on the other side of the island (the side facing the coast), the sediment is deposited. This sediment continues to build up until it creates the sandbar that connects the island to the beach.

Changing Tombolos - Morphology and sediment distribution

Because of the unique shape of tombolos, they tend to be more likely to change over time due to weathering and tides than the regular coastline. Tombolos demonstrate the sensitivity of shorelines. A small piece of land, such as an island can change the way that waves move, leading to different deposition of sediments. Sea level rise may also contribute to accretion, as material is pushed up with rising sea levels. Tombolos are more prone to natural fluctuations of profile and area as a result of tidal and weather events than a normal beach is. Because of this susceptibility to weathering, tombolos are sometimes made more sturdy through the construction of roads or parking lots. The sediments that make up a tombolo are coarser towards the bottom and finer towards the surface. It is easy to see this pattern when the waves are destructive and wash away finer grained material at the top, revealing coarser sands and cobbles as the base.

Features of shoreline change

Longshore drift plays a large role in the evolution of a shoreline, as if there is a slight change of sediment supply, wind direction, or any other coastal influence longshore drift can change dramatically, affecting the formation and evolution of a beach system or profile. These changes do not occur due to one factor within the coastal system, in fact there are numerous alterations that can occur within the coastal system that may affect the distribution and impact of longshore drift. Some of these are:

1. Geological changes, e.g. erosion, backshore changes and emergence of headlands.
2. Change in hydrodynamic forces, e.g. change in wave diffraction in headland and offshore bank environments.
3. Change to hydrodynamic influences, e.g. the influence of new tidal inlets and deltas on drift.
4. Alterations of the sediment budget, e.g. switch of shorelines from drift to swash alignment, exhaustion of sediment sources.
5. The intervention of humans, e.g. cliff protection, groynes, detached breakwaters.

In order to log this earthcache, please send a private message to the cache owner with the answers to the following questions:

1. [REQUIRED] In accordance with the updated guidelinoes from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please post a photo in your log of yourself or a personal item clearly showing you are in the middle of the tombolo to prove you visited the site. 
2. What is the width of the tombolo at the time of your visit (will vary depending on the tide).
3. What type of material is the tombolo made up of?
4. From what you can see and what you have learned above, which direction do you think the longshore current is coming from, NSEW?  Please provide a reason for your answer.
5. What influences will change the appearance of the Tombolo?