Wednesday, May 21, 2008

Our ever-changing shoreline

Tides are the rising and falling of Earth’s ocean surface caused by the gravitational forces of the Moon and the Sun acting on the oceans. When the sun, moon, and Earth are in alignment (at the time of the new or full moon), the solar tide has an additive effect on the lunar tide, creating extra-high high tides, and very low, low tides—both commonly called spring tides.

Right now we are experiencing what appears to be the “spring tides” which are extremely low which means my beach front has increased by several feet, albeit it temporary. While Hurricane Mitch took about 10 feet of beach front from us when it hit we see remnants of it when the low tide occurs. While our low tide and high tide fluctuate at a level of about 3 feet or less, there are some extreme cases in the world: The Bay of Fundy, on the east coast of Canada, features the largest well-documented tidal ranges in the world, 16 meters (53 ft), because of the shape of the bay. Thankfully we don’t experience extremes such as that.

We have a partially sandy beach which is usually covered by washed-up dead sea grass. These unusual marine flowering plants are called seagrasses because the leaves are long and narrow and are very often green, and because the plants often grow in large "meadows" which look like grassland: in other words many of the species of seagrasses superficially resemble terrestrial grasses of the family Posceae. Because these plants must photosynthesize, they are limited to growing submerged in the photic zone, and most occur in shallow and sheltered coastal waters anchored in sand or mud bottoms. They undergo pollination while submerged and complete their entire life cycle underwater. Seagrasses are sometimes labeled ecosystem engineers because they partly create their own habitat: the leaves slow down water-currents increasing sedimentation and the seagrass roots and rhizomes stabilize the seabed.

Sea grass is a big help in cutting down on the wave action of the sea. We are naturally buffered on our beach by the presence in front of our area by two separate reefs and a long Cay directly in front of our house about 1/2 mile away. Along with the sea grasses we receive less destructive waves than some other areas. However, in a large storm this seems negligible.

The sand making up our beach is a beige colored sand unlike some of the white sands of Hawaii or Florida which are made up from limestone. The most common constituent of sand, in inland continental settings and non-tropical coastal settings, is silica (silicon dioxide, or SiO2), usually in
the form of quartz, which, because of its chemical inertness and considerable hardness, is resistant to weathering. Sand particles range in diameter from 0.0625 (or 1/16 mm) to 2 millimeters an individual particle in this range size is termed a sand grain. The next smaller size class in geology is silt: particles smaller than 0.0625 mm down to 0.004 mm in diameter. The next larger size class above sand is gravel, with particles ranging from 2 mm up to 64 mm. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour).

We occasionally have gravel wash up on the beach which is collected for various uses. There are pockets of gravel all around the island which the people collect for the making of concrete along with sand, another vital component of concrete. This gathering of sand/gravel is against the law as environmentally it can be destructive to the beach areas. However, the Municipal often grants permits to people to remove the sand. Most the time however, the authorities cannot be everywhere and the sand is removed with no one the wiser - well, the locals see it happening but it is such a common occurrence that they don’t worry themselves about it. As I said, this can be very destructive for an area and the long term projection of this destruction does not make itself immediately apparent.

The sand on our beach is not the “soft” sand but gritty and in some places there is so much silica that it sticks to the skin with more adherent qualities than regular sand and is bothersome. Fortunately, on our beach, don’t have a high concentration of silica.

When the tides are low a lot of things are exposed that otherwise would not be. Also, during the rising an falling of the tide, a lot of things wash up on the beach. We have had one large milled log deposited on our beach about a year ago. It is about 3’ in diameter and we wanted to drag it up on the land and use it for a table or seat on the beach. However, it was extremely heavy and water logged and, so, we dismissed that idea. Over the past year it has slowly, due to the storms, moved its way down the beach and is now about 500’ from where it started a year ago. Maybe some day it will make it to the end of the island and go off to another island.

Driftwood, bottles, diapers, shells, 1 flip flop, garbage of all types appear on the beach. We have had a decline in the amount of "garbage" that appears on our beach due to the recycling of plastic products and a clean-up campaign run by our Municipal wherein they are teaching people not to litter - once a huge problem. Either way, the beach of our property is continually changing.

You can’t fight the sea nor its progress as it definitely has a mind of its own.


  1. Ihope when we get to Trujillo I can write about our environment as lovingly as you do yours. And I love the great pics.


  2. I'm really glad to hear that the recycling and anti-littering campaign are working. Maybe there is some hope for the rest of us.