Showing posts with label engineered. Show all posts
Showing posts with label engineered. Show all posts

7 Mar 2014

Tales in time: Criccieth Castle

By Marie Powell (Photos by L. L. Melton)

I love castle hopping, and Wales is one of the best places to explore ruins from bygone days. With some 400 castles in about 20,000 square kilometres (8,000 square miles), there's a lot to explore.

Last year I had the chance to see Criccieth Castle, located at the top of a rocky hill overlooking Cardigan Bay, North Wales. According to the Cadw's Criccieth Castle guidebook, the earliest records of the castle date from the 1230s, when Llywelyn ab Iorwerth (Llywelyn the Great) made it a main seat of power in North Wales.

He built the inner ward of the castle, including the twin towers, using a mix of angular stones from the rock around the castle, glacial boulders, with grey mortar made from beach gravel. The D-shaped towers are typical of Welsh native castles, but these twin gatehouses may have also been influenced by castles of the Marcher lords at Cheshire and Montgomery.

The various princes and kings who owned and controlled Criccieth had a hand in adding to its architecture. Although determining the date of a castle ruin might seem straightforward, there is a controversy over who built what part of Criccieth. Experts turn to structural evidence in the ruins to develop their theories and time estimates.

For example, Llywelyn ap Gruffudd (Llywelyn the Last) added an outer ward to the castle. The mortar used in his time is more gravelly, with stones and boulders brought to the site (rather than quarried from the castle rock) along with blue-grey slate. Experts believe the square holes about eight feet from the top mark the height of the towers during the time of the Welsh princes.

Arrow slits that can be seen at the ground level of the towers, as well as at strategic positions throughout the castle, offered a protected spot for archers guarding the castle from attack. Criccieth had several other buildings and towers as well, including one thought to have housed a trebuchet (a machine to throw stones) or a catapult for warding off enemy attacks.

Criccieth fell to Kind Edward I of England in March 1283, and was later held by Edward II (1307-1327) as well. They built up the top of the towers to the height we see today. The square holes held horizontal beams for a fighting platform (or "hourd") projecting from the wall. The English also used castle rock again, but the mortar from this period contains more shells.

Edward II spent over £250 on repairs and refurbishing, according to the guidebook. The castle was finally destroyed in about 1404, during the time of Owain Glyndwr, and was never rebuilt.

A small museum and gift shop at Criccieth tells more of the history and architecture of the castle, with colourful floor plans such as this one.

Another useful resource is the Castles of Wales website, which includes a discussion of the history, geography, architecture, and archaeology of this and other Welsh castles. As well as the guidebook, Welsh Castles by Adrian Pettifer also offers discussion of Criccieth and other castles by area.

Marie Powell is the author of seven books for children, including Dragonflies are Amazing (Scholastic Canada) and a six-book Word Families series (Amicus Publishing). Her second six-book series is expected this fall.


5 Apr 2013

Help Save the Monarch Butterfly!

What’s not to like about monarchs? Their caterpillars are gorgeously striped. Their chrysalises are an otherworldly green bejeweled with glimmering gold. The adults weigh only half as much as a paperclip, yet can migrate thousands of kilometres—and if you’re lucky enough to be in the right place at the right time you can see congregations of thousands. Monarchs can also make blue jays throw up—a delightful tidbit I learned while researching my new book about migration, Is This Panama? (beautifully illustrated by Soyeon Kim!). Sadly, just as the book went to press, bad news arrived: the over-wintering monarch population in Mexico was the lowest ever recorded.
Roosting monarchs (Agunther)
Hundreds of millions of monarchs migrate each fall to warmer areas. Adults that originate in southern Canada can fly more than 4,000 kilometres (2,500 miles) to reach their hibernation grounds in Mexico. It’s a treacherous journey for a delicate butterfly and many die on the way, but every year millions arrive in a mountain forest near Mexico City. Because it would be too difficult to actually count such large numbers, scientists have been measuring the area of forest each year that the butterflies occupy. In 2011 monarchs covered the trees in 2.89 hectares of forest. This past winter they occupied only 1.19 hectares (5 sq. miles)—a drop of 59%!

Though adult monarchs sip nectar from a variety of flowers, their caterpillars are specialist herbivores, which means they depend on a single type of plant for food. In the monarch’s case, these plants all belong to the milkweed family.
Between hatching and forming a chrysalis, monarch caterpillars increase 3,000 times in size. These two caterpillars are in their second and third stages of growth, called instars. (Jan Thornhill)
Milkweeds have evolved elaborate defenses to prevent themselves from being eaten, including uncomfortably hairy leaves, sticky white latex that bleeds from injured tissues, and toxins called cardenolides. Because of the cardenolides, most insects, as well as vertebrates, avoid eating milkweed, but the monarch has evolved to not only tolerate the toxins, it also uses those very poisons to its own advantage by storing them in its own body, which makes even an adult butterfly just as toxic as the plant. The first time a bird, such as a blue jay, eats a monarch, it will vomit a short time later. Though this is of no benefit to the monarch that was eaten, the bird will remember its bad experience and will avoid eating black-and-orange butterflies from then on.

Meanwhile, milkweed plants are continuing to evolve in response to being eaten by caterpillars. Recent genetic research is showing that there is an evolutionary trend in milkweeds towards healing themselves faster than they can be eaten, instead of producing more toxins that might eventually deter caterpillars. 
Monarch caterpillar on milkweed flowers (Jan Thornhill)
Though milkweeds can get along perfectly well without monarchs, monarchs cannot survive without milkweeds. Unfortunately, milkweeds of all varieties are disappearing. Their grassland habitats have been steadily eroding for more than a century due to human development, and recent severe droughts in Texas and the American Southwest have also taken their toll. But another much greater threat has arrived: farmers across North America are now growing corn and soybeans that are genetically engineered to be herbicide resistant. When these “Roundup Ready” crops, developed by a company called Monsanto, are sprayed with glyphosate-based herbicide, almost any plant—other than the corn and soybeans—is killed. The plants that once grew alongside these crops include milkweed, which, until now, had always been plentiful, as well as a multitude of wildflowers that provide nectar for adult butterflies while they’re migrating. One study has shown that between 1999 and 2009 there has been a 90% loss of common milkweeds in the fields treated with these herbicides.* Soon there may be no milkweed in these croplands at all. And no monarchs.


So What Can We Do To Help?

Grow milkweed in your backyard or in your schoolyard:

Grow a “butterfly garden” with plants that provide food for caterpillars and/or nectar for butterflies:

 Learn more about monarchs and share what you learn: http://www.monarchwatch.org

 
Lobby your political representatives to have products made with genetically modified (GM) crops labeled.

*Pleasants, J.M and Oberhauser, K.S.. 2012. Milkweed loss in agricultural fields due to herbicide use: Effect on the Monarch Butterfly population. Insect Conservation and Diversity (March 12, doi: 10.1111/j.1752-4598.2012.00196x)