Reading the Rocks in Cold Spring Harbor, New York
I slipped into my ski jacket and stuffed some gloves deep in my pockets. My mother honked the horn of the car, and I ran out, locking the door behind me. The ride was only about five minutes. As we approached, I could smell the salt air even from inside the warm car. Mom parked the car, and I ran toward the beach. It was cold; the wind was hitting my face and making my cheeks tingle. I walked along the picturesque beach as the sun was setting to the west of me. The waves crashed upon the beach, and there were whitecaps as far as the eye could see. With my head down and my back hunched over, I looked at the rocky sand. I saw a couple of rocks I knew and put them into the bag I had brought along. By the time I knew it, I had so many rocks I filled up the entire bag! The skies grew dark, and my mother called me to go home.
I laid out all the rocks on the kitchen table as the fire from the fireplace blazed next to me. I looked at each one carefully, examining each one's unique features. I discovered that you don't need to read a long, tedious book to learn about the history of Earth. Rocks and fossils provide much of Earth's history. Each rock had its own story to tell.
The region in which the rocks were collected is a beach on the northern part of Lloyd Neck. Lloyd Neck is located on the north shore of Long Island in New York. There are many different landforms on the Neck. There are clay cliffs to the west of my beach. Much of the clay cliffs in the basin area have eroded. Whatever clay there is on my beach I am sure it was deposited on the water's edge by the sea. Unfortunately, each time another big storm hits the north shore another part of history washes away. The waves of Long Island Sound can act like bulldozers eating away the clay and the rocks like locusts in green fields in the spring. However, the ongoing storms do continually supply newly unearthed sediment to the beach. Other important landforms in the area are the large boulders on the beach. These boulders are most likely remains from the glacier that formed Long Island. A glacier is made up of snow and ice. At the end of the Ice Age, the glacier that covered North America melted, advanced, and retreated many times. As they moved, the glaciers dug out Long Island Sound, which was once a valley. The material they carried created a long ridge called a terminal moraine (a terminal moraine marks the line where the glacier finally stops and begins to recede north again). It flowed south and pushed many rocks and boulders in front of it. All of the rocks and boulders on Long Island were from another place. This is how Long Island was formed. Some specific evidences of the existence of glaciers in this area are the chatter marks, or little white marks, found on the rose quartz. These chatter marks were created when other rocks and sediment scraped the rose quartz as the glacier pushed the rocks along.
In the region where I collected my samples, there is a great variety of sedimentary and metamorphic rocks, although there are some igneous rocks, too. Depositing sediment forms a sedimentary rock; sediment is earth that has been sculpted, broken up, and transported by wind, water, or ice. Conglomerate rock found in my sample area is a perfect example of a sedimentary rock. The purple cement that glues the sediment together in the conglomerate rock is called iron oxide (iron and oxygen). Iron oxide can also be an orange color making the rock look like it is rusted. A metamorphic rock is any rock that is transformed by pressure and heat into a rock with new features and minerals. Mica gneiss rock is an example of a metamorphic rock. An igneous rock is made from liquid rock that has cooled. An igneous rock can be volcanic or plutonic. A plutonic rock is formed by the solidification of a molten magma deep within Earth and is crystalline throughout. A volcanic rock is formed by solidification of a molten magma that has poured out as lava over Earth's surface from a volcano or from any surface eruption. The diorite porphyry is an example of an igneous rock.
Here are some descriptions of the rocks I collected:
Rose quartz is a beautiful pink and orange color like a sunset on a summer's eve. It feels as though the sea has washed over it a thousand times and made it smooth as a rose petal. However, there are evident chatter marks that look like white little specks. They look like shredded coconut.
Mica gneiss is a sparkler on the Fourth of July. The bands of minerals in the rock are clearly visible and look like an Oreo cookie. The texture of the rock is like the series of speed bumps in our school parking lot. The mica gneiss is an example of a metamorphic rock.
Red shale is as flat as a penny and as smooth as a gumball inside your mouth. The red shale is a sedimentary rock. Its nickname is Indian paint pot because the Indians that inhabited Long Island used it as war paint and for decorative purposes. The paint can be extracted by rubbing the two stones together and then wetting the stone.
Conglomerate rock is like a hard piece of gum that holds together tons of pebbles. It feels as bumpy as a cobblestone road and is an example of sedimentary rock.
Petrified wood is just like a piece of wood but is surprisingly hard and dense. Millions of years ago during the Cretaceous period, the wood was buried and slowly water containing minerals seeped through the ground. The minerals in the water replaced the wood over time, and the wood became hard rock. The petrified wood may have been buried in the clay cliff for thousands of years until one of the storms ripped it out.
The gneiss rock looks like ripples on the water after a stone is skipped upon the surface. It is a Ruffle potato chip but with bigger ridges. The gneiss is a metamorphic rock.
Granite schist is like a cookie with tons of different chips that represent the many minerals present in the rock. The granite schist is a great example of a metamorphic rock because of the intergrown bands of minerals seen on the side of the rock.
Amphibolite is like a very fine marbleized notebook because of the black and white specks and swirls seen in the rock. Mica is definitely present in the rock because of the glitter specks that catch the light. This is a nice specimen of a metamorphic rock.
Diorite porphyry is an igneous rock. Although we don't have volcanoes on Long Island, the glacier that formed Long Island could have deposited it here from Connecticut, which used to have volcanoes.
Schist is like a shimmery gown worn at a fancy ball. Unlike the granite schist, this rock is a white color.
Long Island is a museum and a laboratory. By studying the rocks of the area, one can discover the tremendous climatic and topographical changes that have taken place over time. Studying the rocks is like watching a dramatic documentary of the physical history of Long Island, but geology is an ongoing science. The beach is a very dynamic system. It is constantly changing as more materials are deposited on its shores. Glaciers produce landforms that are unique and leave behind a wide variety of materials of all sizes (from clay to boulder) and rock type. This variety of materials is discovered only over time. The history of Long Island is not complete. We are discovering new facts every day.
Audubon Society Field Guide to North American Rocks and Minerals. New York: Alfred A. Knopf, Inc., 1979.
The Evolution of L.I. Sound. http://www.lihistory.com/l/hsl04a.html
Tofel, J. E., (1998). Personal interview.
Van Diver, Bradford B. Roadside Geology. Missoula, Montana: Mountain Press Publishing Company, 1985.
More About This Resource...
Less than 1 period
- Tell students that in the essay they are about to read a student learns about the geologic history of her area from the rocks she finds.
- Send students to this online article, or print copies of the essay for them to read.
- Have students work with a partner to select one of the rocks Mary collected.
- Have partners visit this guided exploration of the Hall of Planet Earth to learn more about their rock and how it formed. Have them report their findings to the class.
OriginYoung Naturalist Awards
SubtopicMinerals and Resources