A rock is a solid made up of a bunch of different minerals. Rocks are generally not uniform or made up of exact structures that can be described by scientific formulas. Scientists generally classify rocks by how they were made or formed.

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Three Major Types of Rocks

Metamorphic Rocks – Metamorphic rocks are formed by great heat and pressure. They are generally found in the Earth’s crust where there is enough heat and to form the rocks. Metamorphic rocks are often made from other types of rock. A sedimentary rock can be changed, or metamorphosed, into a metamorphic rocks such as slate or gneiss. Metamorphic rocks include marble, anthracite, soapstone, and schist.

Igneous Rocks – Igneous rocks are formed by volcanoes. When a volcano erupts, it spews out hot molten rock called magma or lava. Eventually, the magma will cool down and harden, either when it reaches the Earth’s surface or somewhere within the crust. This hardened magma or lava are called igneous rocks. Igneous rocks include basalt and granite.

Sedimentary Rocks – Sedimentary rocks are formed by years and years of sediment compacting together and becoming hard. Generally, something like a stream or river will carry lots of small pieces of rocks and minerals to a larger body of water. These pieces will settle at the bottom and over a really long time (perhaps millions of years), they will form into solid rocks. Sedimentary rocks are shale, limestone, and sandstone.

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The Rock Cycle 

Rocks are constantly changing in what is called the rock cycle. It takes millions of years for rocks to change.

1. Melted rocks or magma is sent to the earth‘s surface by a volcano. It cools and forms an igneous rocks.
2. Next the weather, or a river, and other events will slowly break up this rocks into small pieces of sediment.
3. As sediment builds up and hardens over years, a sedimentary rock is formed.
4. Slowly this sediment rocks will get covered with other rocks and end up deep in the Earth’s crust.
5. When the pressure and heat get high enough, the sedimentary rock will metamorphose into a metamorphic rock and the cycle will start over again.

Space Rocks 

There are actually some rocks that come from space called meteorites. They may have different elements or mineral make up than a typical earth rock. Typically they are made up mostly of iron.

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Interesting Facts about Rocks

• The word “igneous” comes from the Latin word “ignis” which means “of fire.”
• Ores are rocks that include minerals that have important elements such as metals like gold and silver.
• Sedimentary rocks form layers at the bottoms of oceans and lakes.
• Marble is a metamorphic rocks formed when limestone is exposed to high heat and pressure within the Earth.
• Layers of sedimentary rocks are called strata.

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Erosion is the wearing away of the land by forces such as  water, the wind, and ice. Erosion has helped to form many interesting features of the Earth‘s surface including mountain peaks, valleys, and coastlines.

There are many different forces in nature that cause erosions. Depending on the type of force, erosions can happen quickly or take thousands of years. The three main forces that cause erosion are water, the wind, and ice.

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Erosion by Water

Water is the main cause of erosions on Earth. Although water may not seem powerful at first, it is one of the most powerful forces on the planet. Here are some of the ways that water causes erosion:

• Rainfall – Rainfall can cause erosions both when the rain hits the surface of the Earth, called splash erosions, and when raindrops accumulate and flow like small streams.
• Rivers – Rivers can create a significant amount of erosions over time. They break up particles along the river bottom and carry them downstream. One example of river erosion is the Grand Canyon which was formed by the Colorado River.
• Waves – Ocean waves can cause the coastline to erode. The sheer energy and force of the waves cause pieces of rock and coastline to break off changing the coastline over time.
• Floods – Large floods can cause erosions to happen very quickly acting like powerful rivers.

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Erosion by Wind

The Wind is a major type of erosion, especially in dry areas. The Wind can erode by picking up and carrying loose particles and dust away (called deflation). It can also erode when these flying particles strike the land and break off more particles (called abrasion).

Erosion by Glaciers

Glaciers are giant rivers of ice that slowly move carving out valleys and shaping mountains.

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Other Forces

• Living organisms – Small animals, insects, and worms can add to erosions by breaking up the soil so it is easier for the wind and water to carry away.
• Gravity – The force of gravity can cause erosions by pulling rocks and other particles down the side of a mountain or cliff. Gravity can cause landslides which can significantly erode an area.
• Temperature – Changes in temperature caused by the Sun heating up a rock can cause the rock to expand and crack. This can cause pieces to break off over time and lead to erosions.

Human activity has increased the rate of erosions in many areas. This happens through farming, ranching, cutting down forests, and the building of roads and cities. Human activity has caused about one million acres of topsoil to erode each year.

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Erosion Control

There are things that can be done to limit the amount of erosions caused by human activity. This includes planting trees around farmland to protect it from the wind, moving herds around so that grasslands will grow back, and planting new trees to replace the ones cut down.

Interesting Facts about Erosion

• The word erosion comes from the Latin word “erosion em” which means “a gnawing away.”
• Scientists estimate that the Colorado River has been eroding the Grand Canyon for many millions of years.
• Wind erosions can cause huge dust storms.
• The fastest glacier ever moved over seven miles in three months.
• Fossils in sedimentary rock are often uncovered by erosions.

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Topography

The water cycle is a way that water moves all around the Earth. It never stops and doesn’t really have a beginning or an end. It’s like a big circle. We’ll describe it by starting with water that’s on land. For example, water in the ocean or a lake. Some water on the surface of the ocean will evaporate due to heat from the sun. When it evaporates it turns into vapor water and goes up into the atmosphere.

This vapor water gets together with a lot of other vapor water and turns into clouds. Clouds move about the earth with the weather and once they are so full of water they drop the water to Earth in some form of precipitation. It could be rain, snow, sleet, or hail. When the water hits the earth it may fall right back into the ocean or feed a flower or be snow on the top of a mountain. Eventually, this water will evaporate and start the whole cycle again.

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There are three main ways that water on land turns into vapor:

Evaporation – This is the main process by which water goes from the ground to vapor in the atmosphere. Around 90 percent of the water vapor in the atmosphere got there through evaporation. Evaporation takes place only on the water’s surface. It takes energy in the form of heat. Hot water will evaporate more easily than cold water. The sun provides a lot of the energy for evaporation in the water cycle, primarily causing evaporation from the surface of the ocean.

Sublimation – This is when water moves directly to vapor from ice or snow without ever melting into water. Good conditions for sublimation to occur is when ice or snow is in very cold conditions, but it is windy and the sun is shining.

Transpiration – Transpiration is when plants release water to their leaves that then evaporates into vapor. Plants will release a lot of water as they grow. Around 10 percent of the water vapor in the atmosphere is estimated to come from transpiration.

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Water in the atmosphere

We see water in the atmosphere in the form of clouds. There is a small amount of water even in clear skies, but clouds are where water has started to condense. Condensation is the process of water vapor becoming liquid water. Condensation is a major step in the water cycle. The atmosphere helps to move water around the world. It takes water that evaporated from the ocean and moves it over land where clouds and storms form to water plants with rain.

Precipitation

Precipitation is when water falls from the atmosphere back to land. Once enough water gathers in a cloud droplet of water will form and fall to the earth. Depending on the temperature and weather this could be rain, snow, sleet, or even hail.

Water storage

A lot of the Earth’s water does not take part in the water cycle very often. Much of it is stored. The Earth stores water in a number of places. The ocean is the largest storage of water. Around 96 percent of the Earth’s water is stored in the ocean. We can’t drink the salty ocean water, so fortunately for us, freshwater is also stored in lakes, glaciers, snow caps, rivers, and below the ground in ground water storage.

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• Marco Polo (1254-1324):

Italian traveler Marco Polo was one of the first European to visit China and other far eastern territories. However, his reports were not believed but he encouraged the idea of trading with the East. His father and uncle were a merchant which inspired Polo to overcome the deep concepts of appraising, foreign currency and handling cargo ships.

• John Cabot (1450-98):

Italian-born explorer John Cabot was employed by British merchants to seek a western route to Asia. During his travels, he discovered parts of the northeast coast of America. He was also sponsored by the Great Britain to start an expedition for exploring the Atlantic.

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• Christopher Columbus (1451-1506):

This Genoese colonizer discovered North, Central and South America and the islands of West Indies. It was Columbus who established the string between indigenous Americans and Europeans. As a phenomenon of culture and civilization, Columbus will be always remembered for discovering the “New World”.

• Vasco da Gama (1460-1524):

Considered as the greatest hero in the European age of discovery, Portuguese explorer Vasco da Gama traveled round the Cape of Good Hope and up the East coast of Africa and later discovered a trade route to India. After mastering in the field of mathematics and navigation he became the governor of Portuguese India in 1524.

• Ferdinand Magellan (1480-1521):

Magellan was a Portuguese explorer who led the first voyage around the world. He discovered the Strait of Magellan, near the tip of South America. He was born in Sabrosa but later adopted the nationality of Spain to serve King Charles I in order to explore the westward route to the Spice Island.

• Abel Tasman (1603-59):

This Dutchman was an aesthetic voyager and is notable for exploring Australia, New Zealand and Van Diemen’s Land (later called Tasmania). With his ships Heemskerck and Zeehaen , Tasman led the exploring expedition towards North Pacific with the object to obtain knowledge of all undiscovered beaches in the world.

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• Henry Hudson (1550-1611):

Henry Hudson was an English navigator who searched for a Northwest Passage (a route to the east by traveling north of America) and discovered Hudson’s Bay. He is also credited to discover the area around modern New York City while exploring the route to Asia via west.

• James Cook (1728-79):

Famous British Captain James Cook led several major expeditions. He explored the coasts of Australia, New Zealand, and North America. An epitome in the area of geographical exploration, Captain Crook was killed in 1779 by Hawaiians during his third exploratory navigation.

• David Livingstone (1813-73):

Livingstone was a Scottish missionary and explorer of Africa. He discovered and named the Victoria Falls after Queen Victoria. Encourager of commercial empire, Livingstone was born in a protestant family and his father was much institutionalized to his beliefs.

• Sir Richard Burton (1821-90):

Son of a British army officer, Sir Burton is best known for exploring Arabia and Lake Tanganyika in Africa. Strictly denying the colonial policies, he served for seven years in India as a captain in the army of “East India Company”. This controversial poet is also credited for translating “One Thousand And One Nights” .

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