Comprehensive Guide To Substances Found In The Earth

The earth is filled with a diverse array of natural resources that modern civilization depends on. From the fossil fuels that power our homes to the precious metals used in electronics, many of the items we use every day originate deep underground.

If you’re short on time, here’s a quick answer to your question: The most common substances found in the earth include water, rocks, minerals, fossil fuels like oil and coal, and soil.

In this comprehensive guide, we will explore the major categories of substances found in the earth’s crust, mantle, and core. We will look at how these materials are formed, where they are located, how humans harvest them, and their numerous applications in industry, technology, and everyday life.

The Composition of the Earth

The Crust

The Earth’s crust is the outermost layer that ranges from 3 to 45 miles in depth depending on the location. It is composed of lighter rocks like granite and basalt and makes up less than 1% of the planet’s total volume.

The crust is brittle and broken into massive sections called tectonic plates that slowly move and interact, causing earthquakes and volcanic eruptions. Understanding the composition and dynamics of the crust is key to predicting seismic hazards and identifying resources like precious metals and fossils.

The Mantle

Beneath the crust lies the mantle, which extends 1,800 miles down and makes up a whopping 84% of the Earth’s volume. This extremely hot layer consists of rigid rock composed mainly of magnesium, iron, silicon, and oxygen compounds.

Convection currents in the mantle, where heat causes material to rise and sink in a circular pattern, are what drive the movement of tectonic plates at the surface. Volcanoes form when superheated mantle rock from below melts and erupts through weak points in the crust.

The Core

At the heart of our planet lies the core, which has two distinct parts. The liquid outer core is about 1,400 miles thick and has a composition high in iron and nickel. Importantly, the churning of molten metal in this layer generates the Earth’s magnetic field.

The inner core is a solid iron ball approximately 750 miles across that formed as the planet cooled. With immense heat and pressure conditions matching those on the sun, analyzing the ancient inner core gives clues into how Earth originated 4.5 billion years ago.

From the inhabited crust we call home to the remote inner core, each layer of our planet has a unique composition and properties essential to life on Earth. As geologists further probe deep underground and improve imaging techniques, we continue to unravel the mysteries hidden within this dynamic, intricately layered sphere.

Water

Sources of Water

Water is one of the most abundant resources on Earth, covering over 70% of the planet’s surface. The main sources of water are:

• Oceans – The oceans contain around 96.5% of all Earth’s water. Seawater is salty and undrinkable without desalination.
• Ice caps and glaciers – About 68.7% of freshwater on Earth is frozen in the ice caps and glaciers, like Antarctica and Greenland. This source provides drinking water when the ice melts.
• Groundwater – Underground stores of water fill cracks and spaces in soil, sand, and rock. Groundwater supplies wells and springs and has been deposited by precipitation over thousands of years.
• Freshwater lakes – Only about 0.3% of Earth’s freshwater is found in surface lakes and rivers. The Great Lakes in North America contain 21% of the world’s surface freshwater.
• Atmosphere – The air contains about 0.04% of Earth’s water in the form of vapor, clouds and precipitation. This source is renewed through evaporation and precipitation.

Other minor sources include soil moisture, swamp water, permafrost, and even plants and animals. Water is continuously cycled through the earth’s ecosystems through the water cycle of evaporation, condensation, and precipitation.

Uses of Water

Water has many important uses, being essential for life on Earth. The main uses of water are:

• Drinking – Water is crucial for hydration and health. The average human needs to drink at least 64 ounces of water per day.
• Sanitation – Clean water provides hygiene and prevents disease when used for washing, cooking and cleaning.
• Agriculture – 70% of worldwide water use is for irrigation and agriculture. Water is essential for food production.
• Industry – Factories and power plants use water for processing, cleaning, transportation, and cooling purposes.
• Leisure – Water-based recreation includes swimming, boating, fishing and water sports.
• Habitat – All ecosystems require water from ponds, rivers, wetlands to oceans.

Some key statistics on global water usage:

Water is a unique substance vital for all life. Without water, life as we know it could not exist. This indispensable resource must be carefully managed to provide for both human and environmental demands. For more information, visit the U.S. Geological Survey and Natural Resources Defense Council.

Rocks and Minerals

Igneous Rocks

Igneous rocks form when molten rock (magma or lava) cools and solidifies. The minerals in the rock crystallize as the magma cools. Igneous rocks can have large crystals (intrusive igneous rocks) or small crystals (extrusive igneous rocks).

Common intrusive igneous rocks include granite, diorite, gabbro, and pegmatite. Common extrusive igneous rocks include basalt, obsidian, pumice, and scoria. Igneous rocks make up most of the oceanic and continental crusts.

Sedimentary Rocks

Sedimentary rocks form from the accumulation and cementation of mineral and organic particles on the Earth’s surface and within bodies of water. The particles accumulate in layers and cement over time to form solid rock. Sedimentary rocks include shale, sandstone, limestone, and conglomerate.

Fossils are often found in sedimentary rock. Sedimentary rocks make up only 5% of the crust but they cover 75% of the surface. That’s because igneous and metamorphic rocks are uplifted and eroded while sedimentary rocks are deposited in lower elevations like oceans.

Metamorphic Rocks

Metamorphic rocks form when existing rocks are changed by heat, pressure, or reactive fluids. The minerals in the original rock recrystallize under these conditions to form a new rock with different mineral composition and texture. Common metamorphic rocks include slate, schist, gneiss, and marble.

Regional metamorphism happens to large areas when mountain belts are formed. Contact metamorphism occurs next to igneous intrusions. Metamorphic rocks make up most of the continental crusts and ocean floors.

Minerals

Minerals are naturally occurring inorganic compounds with a crystalline structure and defined chemical composition. Over 4,000 minerals have been discovered so far. Some common rock-forming minerals include quartz, feldspar, amphibole, pyroxene, olivine, calcite, and clay minerals.

Economic minerals that are mined for profit include ores of iron, aluminum, copper, tin, lead, zinc, nickel, silver, and gold. Gemstones like diamonds, emeralds, and rubies are also minerals. Overall, minerals are essential building blocks of rocks and contribute greatly to the Earth’s beauty.

Fossil Fuels

Coal

Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons. It is formed from vegetation that has been consolidated between other rock strata and altered by the combined effects of pressure and heat over millions of years to form coal seams.

Coal is the largest source of energy for generating electricity worldwide, as well as an essential raw material for the production of steel and cement. According to the U.S. Energy Information Administration, coal accounted for about 23% of the electricity generation worldwide in 2021.

The different types of coal include anthracite, bituminous, subbituminous, and lignite. Anthracite is the hardest coal and contains the highest amount of carbon, lending to its higher heating value compared to the other types of coal.

Bituminous coal has lower carbon content but also has a relatively high heating value and is the most abundant type of coal globally. Subbituminous coal has 35-45% carbon content, while lignite (also called brown coal) has 25-35% carbon and the lowest heating value.

China produces and consumes more coal than any other country, while the U.S., India, Australia, and Indonesia are also major coal producers.

While coal has played an important role in the Industrial Revolution and electricity generation for decades, burning coal emits harmful air pollutants like carbon dioxide, sulfur dioxide, nitrogen oxides, mercury, and particulate matter. Coal mining can also damage local environments and ecosystems through land disturbances.

Many countries are now implementing policies to phase out coal power and transition to cleaner energy sources like natural gas, solar, and wind.

Oil

Crude oil, often simply called oil, is a liquid fossil fuel found underground that can be refined into fuels like gasoline, diesel, and many other products. Oil is formed from the remains of ancient marine organisms that died millions of years ago and were buried under layers of sediment.

Over time, heat and pressure turned the organic matter into hydrocarbons. Exploratory drilling is used to locate oil deposits, which are then extracted and refined.

The top oil-producing countries are the United States, Saudi Arabia, Russia, Canada, and Iraq. However, countries in the Middle East hold the majority of proven oil reserves. Oil powers the transportation sector globally and is also used as a fuel for heating and generating electricity.

Petrochemicals derived from petroleum provide materials to manufacture plastics, fabrics, solvents, and fertilizers.

While oil has enabled incredible economic and industrial growth over the past century, burning oil products like gasoline and diesel releases greenhouse gases that contribute to climate change. Oil spills during extraction and transport can also harm marine ecosystems.

Many experts believe oil production has already peaked or will do so in the coming decades as reserves deplete. The electrification of transportation and growth of renewables may reduce oil demand in the long term.

Natural Gas

Natural gas is a fossil fuel comprised almost entirely of methane and is found in deep underground reservoirs of porous rock. It is formed by the same geological processes that form oil. Natural gas can also be harvested as a byproduct during crude oil drilling.

Advances in horizontal drilling and hydraulic fracturing techniques have unlocked vast new shale gas resources in recent decades.

Natural gas emits 50-60% less carbon dioxide when burned compared to coal, so it produces less pollution. About 1⁄4 of U.S. electricity was generated by natural gas in 2021. It is also used to heat buildings and as an industrial feedstock.

Liquefied natural gas (LNG) allows efficient transport of gas globally via tankers.

The top natural gas producers are the U.S., Russia, Iran, Qatar, and Canada. Proven global reserves are abundant and production capacity continues to grow. Natural gas will likely overtake coal as the world’s second largest energy source behind oil in the coming years.

However, methane leaks during gas drilling and transport may offset some of its environmental benefits vs. coal. Renewables are still a cleaner option long-term.

Soil

Composition of Soil

Soil is composed of minerals, organic matter, water, air and living organisms. The components can be divided into solid, liquid and gaseous phases. The solid phase makes up around 45% of the volume and is composed of both inorganic and organic materials.

The inorganic component contains the non-living minerals and accounts for around 40% of soil volume. This includes sand, silt and clay particles of varying sizes. Sand particles are the largest in size from 0.05 to 2 mm, silt ranges from 0.002 to 0.05 mm and clay is less than 0.002 mm.

The organic solid phase contains decaying leaves, microorganisms and humus. This living and decomposing material accounts for around 5% of the soil’s volume.

The liquid phase is composed of soil water and contains dissolved nutrients and minerals. This accounts for 20-30% of the soil’s pore space volume. The final gaseous phase contains trapped air and accounts for 10-30% of the pore space.

The pore space allows room for water drainage and aeration which are vital for plant growth.

Soil Layers

There are 5 major layers that make up a typical soil profile. These layers are:

• O Horizon – This is the top organic layer composed of decomposing leaves, twigs and animal matter.
• A Horizon – This layer contains the humus, which is organic matter, and eluviation, which is the loss of clay, iron and aluminum compounds that have been leached downward.
• E Horizon – This is the zone of eluviation containing sand, silt and resistant materials like quartz.
• B Horizon – This layer contains illuviated clay, iron and aluminum compounds that have leached down from above layers and accumulated here.
• C Horizon – This bottom layer consists of loose rock particles and partially weathered parent material.

The O, A and E horizons are considered the topsoil layers where most biological activity occurs. The B horizon is termed subsoil and contains clay accumulations while the C horizon consists of unconsolidated parent material.

Soil Nutrients

The major nutrients required for plant growth in soil are nitrogen, phosphorus and potassium. Nitrogen is required for leaf growth and is either added naturally by nitrogen-fixing bacteria or synthetically through fertilizers. Phosphorus aids in root development, plant maturation and flowering.

Potassium promotes strong root systems and increases drought tolerance. Other nutrients essential in smaller amounts are calcium, magnesium and sulfur.

Micronutrients such as iron, chlorine, zinc, boron, manganese, copper and molybdenum are only required in trace amounts but are vital to plant health and growth. Deficiencies in any of these can cause major crop issues.

Soil tests are done to determine the levels of both macro and micronutrients and any amendments needed for optimal plant growth.

Both organic and inorganic fertilizers can be added to soils to correct any deficiencies that exist and improve overall soil health and productivity. Proper management of soil nutrients is crucial for optimal plant growth and crop yields.

Conclusion

From the air we breathe to the homes we live in, we depend on the resources found within the earth each day. By understanding the complex composition of our planet and the processes that concentrate valuable materials, we can more responsibly harvest these resources while conserving them for future generations.

The earth’s crust, mantle, and core contain a vast diversity of vital substances like water, rocks, minerals, fossil fuels, and soil. Each has played an integral role in the development of human civilization.

As our knowledge grows, so too can our stewardship of the limited resources granted to us by our planetary home.