Igneous Rocks

The first rocks to form on earth probably looked much like the igneous rocks that harden from lava today. Igneous rock is any rock that forms from magma or lava. The name “igneous” comes from the Latin word ignis, meaning The first rocks to form on earth probably looked much like the igneous rocks that harden from lava today. Igneous rock is any rock that forms from magma or lava. The name “igneous” comes from the Latin word ignis, meaning “fire”.

Meet IGGY “Iggy” is an igneous rock. He is here to let us know that he can form in one of two ways. Not only can he form from large impressive volcanic explosions but also more slowly, less dramatic ways under the earth.

Most igneous rocks are made of mineral crystals. They are formed Extrusively or Intrusively.

~ Extrusive Rock is igneous rock formed from lava that erupted onto the Earth’s surface. ~ Basalt is the most common extrusive rock. Basalt forms much of the oceanic crust, shield volcanoes, and lave plateaus.

Meet “Bubbles” Basalt, a relative of Iggy. She is fine grained and contains some large crystals. Bubbles has a bubbly surface. She is dark gray with black, dark brown and reddish brown tones. She is found any where volcanoes are or have been active. Mostly consists on the oceanic and continental crusts.

Intrusive Rock is igneous rock that formed when magma hardened beneath Earth’s surface. Granite is the most abundant intrusive rock in continental crust. This occurs when magma flows away from the volcanic activity to another place underground where it cools slowly inside the earth.

Meet “Giant” Granite, another relative of Iggy. He has large particles that are easily seen and is a speckled light and dark color. Giant is typically white to gray, pink or red. Found largely in the continental crust especially throughout the mountains of North America.

Igneous rocks are hard, dense and durable. People throughout history have used igneous rock for tools and building materials Example: Native Americans used obsidian for making very sharp tools Granite has a long history as a building material.

Sedimentary Rocks

Meet SED: Sed is a sedimentary rock. He is here to let us know that he is formed from small particles of rock and other debris that get squashed together. He is really cool with any sediments that come his way. He will accept any particle no matter how far it may have traveled. Lay it On me, man……

~ Sedimentary rocks form from particles deposited by water and wind. ~ Along the beach, a stream you will see tiny sand grains, mud and pebbles. These are what make up sedimentary rocks. ~ Water, wind and ice will carry the sediments, depositing them in layers.

Erosion: ~ Destructive forces such as heat and cold, rain, waves and grinding ice are constantly breaking up and wearing away all the rocks on surface. ~ rushing water or wind loosen will carry away the fragments of rock. Water

Deposition: is the settling out of the sediments after it has been carried away by wind or water. ~ If in water, the water will slow and allow the sediments to drop to the bottom of a river or lake. ~ Sediments may include: shells, bones, leaves, stems and other remains of living things. ~ These living things will eventually settle, slowly harden and change into fossils.

Compaction: ~ At first the sediments fit together loosely. But gradually, over millions of year, thick layers of sediment build up. These are layers are heavy and press down on the layers beneath them. ~ This is compaction. ~ These layers are easy to see in rock.

Meet “Sandy” Sandstone: Cousin to Sed, she is fine to medium particle shaped and it a gray to red to brown color. She loves the ocean as she typically forms from the sand on the beach, ocean floor, river beds or even in sand dunes. She comes together nicely through the after getting compacted then cemented together with other fine particles like her self.

Meet “Smooth-Talkin’” Shale: Another cousin to Sed, “smooth talkin’” is made of fine grains and particles that are not visible, and yes he even contains fossils. He is a smooth gray, or brown or sometimes a reddish brown. Shale is so smooth because he is made of clay. He forms when water deposits clay in very thin, flay layers one on top of each other. While is smooth he can be spit easily

Meet “Bones” Limestone: Cousin to Sed, “Bones” is fine grained with a pitted, crumbly-looking surface that may contain fossils. He is light gray to dark gray and on the rare occasion a yellow or brown. He is an ocean lover because many living things like coral, oyster, snails, shells or skeletons pile up as sediments on the ocean floor. Over Millions of years these layers grow as deep as hundreds of meters. Weight of the layers builds up and squashed “Bones” together.

So our rock started off being blasted out of a volcano and ended up as a grain of sand that turned into a sedimentary rock. It could simply stay as a sedimentary rock or it could get hotter and hotter and be under more and more pressure so that he has to “morph”.

Metamorphic Rocks

~ Heat and pressure deep beneath Earth’s surface can change any rock into metamorphic rock. ~ Collisions between earth’s plates can push the rock down toward the heat of the mantle. ~ Pockets of magma pushing up through the crust also provide heat. ~ The deeper the rock is buried the more pressure it placed on the rock. The minerals in the rock can change into other minerals.

Some Metamorphic rock will foliate: meaning they become thin and flat, leaf like.

Meet “Morph”: Whoa, I’m hot! I can’t take all this pressure! How much more time do I have to spend here?