coquina - the rock that saved st augustine fr...
coquina - the rock that saved st augustine from national park service\nthe adaptation of new raw materials was an ongoing challenge for the europeans who came to the new world. in this essay, the author describes how the discovery of a new building material was used to construct an old building type, and in the process, helped the spanish maintain their hold on florida.\na fort made out of seashells?\n(1) who would think that a fort made of seashells would last 300 years? who would think that a fort made out of seashells would last three days under cannon fire? but the castillo de san marcos, made of local coquina stone, did just that. what exactly is this strange rock? how was it formed, and where did it come from? and how did this rock shape the history of st. augustine?\nhow coquina is formed\n(2) thousands of years ago, the tiny coquina clam (donax variabilis) lived in the shallow waters of coastal florida, as they still do today. these are the small pink, lavender, yellow, or white shells one sees along the beach at the waterline. as the resident clam died, the shells accumulated in layers, year after year, century after century, for thousands of years, forming submerged deposits several feet thick. during the last ice age, sea levels dropped, exposing these shell layers to air and rain. eventually, the shell became covered with soil, then trees and other vegetation. rainwater percolating through the dead vegetation and soil picked up carbon dioxide and became carbonic acid, the same ingredient that makes soda fizz.\n(3) as this weak acid soaked downward, it dissolved some of the calcium in the shells, producing calcium carbonate, which solidified in lower layers, much like how flowstone and stalactites are formed in caves. this material \glued\ the shell fragments together into a porous type of limestone we now call coquina, which is spanish for \tiny shell.\\na stronger fort is needed\n(4) although found in very few places in the world, conditions were just right for coquina formation along the east coast of florida. the spanish knew about this rock, and while they might have picked up loose chunks, the people of st. augustine were primarily soldiers, not stonemasons, and so this rock sat mostly unused and unappreciated for years. wood was more plentiful, at first, and easier to work with. but then the british, settling to the north, edged into the carolinas. spanish florida was only a short sail away. something more than a wooden fort was needed to protect st. augustine and to keep the british from taking over florida.\n(5) as a result, the spanish began construction on the castillo de san marcos in 1672. the coquina stone was quarried in the area of present - day anastasia state park on anastasia island. military engineers and stonemasons were brought from spain. oyster shells were burned into lime.\nselect the correct answer.\nbased on paragraph 3, what is true about calcium carbonate?\na. it is made from limestone.\nb. it helps bond materials together.\nc. it dissolves calcium in shells.\nd. it solidifies when placed in caves.