Earth Structures

Marble is a metamorphic rock made from:

limestone

Flat Earth

Many ancient civilizations believed the earth was flat. However, it did not take long for scientists and philosophers to question this flat model. The Greek philosopher Aristotle used logic and physical evidence to prove the spherical shape of the earth. He reasoned that the earth was round because the shadow seen crossing the moon during an eclipse is curved. Aristotle also pointed out that a person in the North does not see the same stars as a person in the South.

Igneous rock are made from:

Melted Minerals

Categories of rock

The three main categories of rock in the earth's crust are igneous,sedimentary, and metamorphic. Igneous rocks were originally molten; then they were formed by cooling. Sedimentary rocks were laid in place primarily by moving water. Metamorphic rocks are formed from pre-existing igneous or sedimentary rocks that were subject to intense heat and/or pressure.

Which of the following is an igneous rock?

granite

Metamorphic rock are changed by:

heat and pressure

Igneous rocks are formed from:

magma

Stalactites in caves are:

precipitate sedimentary rocks

Which of the following is a sedimentary rock?

shale

What type of cooling would a scientist determine formed an igneous rock found with large crystals?

slow cooling

Astronomy in the Middle Ages:

Astronomy in the Middle Ages followed the teaching of the first-century Greek-Egyptian author, Ptolemy. Ptolemy was incorrect that the sun and other planets circled the earth. He was correct when he described the earth as a sphere with an equator, North Pole, and South Pole.Later findings would reveal that there are many heavenly bodies that revolve around the sun to make up our solar system. This system, made up of one star and nine planets, is held together by the force of gravity. The sun's gravity pulls on each of the planets to keep them in orbit. Gravity is also the force that keeps each planet's moons orbiting around them. There is a gravitational pull on both the moon and Earth. There are mountains and craters on both.

Eratosthenes

Eratosthenes was a Greek scientist who lived in Egypt, is usually credited as the first to calculate the circumference of the earth. At noon on the first day of summer, he measured the angle of the sun's rays at Alexandria and at Syene (Aswan), both in Egypt. Since the difference in angle was almost one-fiftieth of a circle, the earth's circumference was 50 times the distance between the towns. According to his calculations, the circumference was about 25,000 miles. His measurement was remarkably close to the earth's actual circumference.

Education in the Middle Ages

From the fourth to the fourteenth centuries, kings in Europe held a globe to represent the world in their hands during their coronation ceremonies. Textbooks used in monastery and cathedral schools, as well as in later medieval universities, agreed that the earth was a sphere.

What did Eratosthenes do?

He calculated the circumference of the earth

Igneous rock

Igneous rocks are the oldest rocks on earth. They make up the ocean floor and the bottom of many mountains. These rocks are made from hot, melted minerals deep inside the earth. The melted minerals are called magma. When magma cools, it hardens. Hardened magma becomes igneous rock. Most of the time, magma cools inside the earth. Over time, rocks on the surface are eroded and the igneous rocks show. Sometimes, magma cools outside on the surface. This happens when volcanoes erupt and let magma pour out. Magma on the surface is called lava. Igneous rocks are made of crystals. The crystals can be large or small. The size of crystals depends on how fast the magma cools. Slow cooling makes large crystals. Granite and gabbro are igneous rocks with large crystals. Fast cooling makes small crystals. Balsalt is a rock with small crystals. Obsidian is a rock that cools so quickly it has no crystals at all.

Evan finds a rock while hiking. It has a fossil in it. The rock is most likely a(n):

Sedimentary

Sedimentary rock

Sedimentary rock usually forms near or in water. These types of rocks have layers instead of crystals. In some rocks, these layers look like stripes. There are two basic types of sedimentary rocks - clastic and precipitate.When land is eroded, tiny pieces are carried away by wind and water. These pieces are called sediment. They are dropped off in oceans, seas, and lakes during deposition. Over many years, sediment hardens and becomes new rock. This type of sedimentary rock is called clastic. Precipitate sedimentary rock is made from chemicals dissolved in water. Sometimes, the chemicals separate from the water and settle to the bottom. This process is called precipitation. The stalagmites and stalactites in caves are precipitate sedimentary rocks. Sometimes, sedimentary rocks have fossils inside. Animals and plants that get stuck in wet sediment die and leave behind bones, shells, and prints. Some sedimentary rocks look like a bunch of rocks stuck together with glue. These rocks are called conglomerates. They are a type of sedimentary rock. Limestone, sandstone, and shale are examples of sedimentary rocks. Three quarters of the earth's land surface is covered with distinct layers of sedimentary rock. They range in thickness from a thin layer of perhaps a few hundred feet to over 10,000 feet.

Metamorphic rock

Some rocks have crystals and layers. These rocks are formed from igneous and sedimentary rocks. Heat and pressure change these rocks into metamorphic rocks. The word metamorphic comes from the Greek words meta and morph. Meta means "change", and morph means "shape." When rocks are buried, they get pushed into the Earth by the weight of the rocks above them. These rocks heat up as they move closer to the magma below the surface. Over time, the heat and pressure change the rock. Think of chocolate chip cookie dough. Before it is baked, the chocolate chips are hard and easy to pick out of the dough. When the dough is baked, the chips melt. It is much harder to pick chips out of a baked cookie. The baked cookie is made differently than the unbaked one. This is similar to what happens to a metamorphic rock. Heat and pressure change an igneous or sedimentary rock into something different. Marble, quartzite, and slate are examples of metamorphic rock. Marble is made from limestone, and quartzite is made from sandstone. Slate is made from shale.

Sedimentary rock are made from:

eroded land

Rocks that are melted by heat and then cooled are classified as:

igneous

Sedimentary rocks usually form near:

water