AGRICULTURAL SCIENCE

THEME: AGRICULTURE ECOLOGY 

CLASS – SENIOR SECONDARY SCHOOLS (SS 1) 

 

TOPIC – ROCK FORMATION

LEARNING AREA

1. Meaning and Types of Rocks

2. Economic Importance of Different Types of Rocks

3. The Processes of Each Type of Rock Formation

 

PERFORMANCE OBJECTIVES 

By the end of the lesson, most of the students should have attained the following objectives –

1. describe the processes of each type of rock formation.

2. identify and discuss the meaning and economic importance of different types of rocks.

3. summary the processes of rock formation.

 

INSTRUCTIONAL MATERIALS

The teacher will teach the lesson with the aid of:

1. Laboratory

2. Charts and pictures of different types of rock

3. Field trips to rocky areas

 

REFERENCE MATERIALS

1. Scheme of Work

2. National Curriculum SSS Classes

3. Course Book

4. All Relevant Material

5. Online Information

 

CONTENT OF THE LESSON

INTRODUCTION

Rock is a naturally occurring solid mineral or mineral-like substance formed by geological processes. Rocks are typically composed of one or more minerals or mineraloids, and can vary greatly in appearance, composition, and texture.

 

TYPES OF ROCKS

Rocks also play a vital role in shaping the Earth’s surface and geological history. There are three major types of Rocks – Metamorphic, Igneous, and Sedimentary rocks. Each type of rock has its own distinct characteristics and properties, making them valuable resources for construction, manufacturing, and scientific research. 

They are classified into three main types based on how they are formed:

1. IGNEOUS ROCKS

Igneous rocks are formed by the solidification of molten rock material, either within the Earth’s crust (intrusive) or on the surface (extrusive). Examples of common igneous rocks include granite, basalt, and pumice.

2. SEDIMENTARY ROCKS

Sedimentary rocks are formed by the accumulation and cementation of sediments such as sand, silt, and clay, or by the precipitation of minerals from water. Examples of common sedimentary rocks include limestone, sandstone, and shale.

3. METAMORPHIC ROCKS

Metamorphic rocks are formed from pre-existing rocks (igneous, sedimentary, or other metamorphic rocks) that have been subjected to high pressure, temperature, or chemical changes. Examples of common metamorphic rocks include marble, slate, and schist.

 

IGNEOUS ROCKS

Igneous rocks are formed through the cooling and solidification of magma or lava. They are one of the three main types of rocks, along with sedimentary and metamorphic rocks. Igneous rocks are classified into two main categories: intrusive (plutonic) rocks, which form beneath the Earth’s surface, and extrusive (volcanic) rocks, which form on the Earth’s surface.

 

CHARACTERISTICS/PROPERTIES OF IGNEOUS ROCKS

Igneous rocks are diverse in their composition and characteristics, with each type of rock providing valuable insights into the Earth’s geological history and processes.

1. Composition – Igneous rocks are primarily composed of minerals such as quartz, feldspar, mica, and olivine. The composition of these minerals can vary, leading to different types of igneous rocks with unique characteristics.

2. Texture – The texture of igneous rocks is determined by the size and arrangement of mineral grains. Igneous rocks can have either a coarse-grained texture, where mineral grains are visible to the naked eye, or a fine-grained texture, where mineral grains are too small to see without a microscope.

3. Color – Igneous rocks can come in a variety of colors, depending on their mineral composition. For example, felsic rocks tend to be light-colored, while mafic rocks are typically dark-colored.

4. Crystal Form – Igneous rocks can sometimes form crystals as they cool and solidify. These crystals can range in size and shape, and their presence can help geologists determine the cooling history of the rock.

5. Hardness – Igneous rocks are generally hard and durable, making them suitable for use as construction materials.

6. Density – Igneous rocks are typically denser than sedimentary rocks, due to their crystalline structure and mineral composition.

7. Formation – Igneous rocks are formed through the cooling and solidification of magma or lava. The rate of cooling can influence the texture and mineral composition of the rock.

 

ECONOMICS IMPORTANCE OF IGNEOUS ROCKS

1. Igneous rocks are a major source of various economically important minerals such as copper, gold, silver, uranium, and rare earth elements. These minerals are used in various industries such as construction, electronics, and manufacturing.

2. Igneous rocks play a crucial role in the development of geothermal energy resources. Hot rocks beneath the Earth’s surface can be tapped to generate power, providing a renewable and clean energy source.

3. Igneous rocks like granite, basalt, and diorite are commonly used as building materials due to their durability and strength. These rocks are used in construction projects such as buildings, bridges, and roads.

4. Igneous rocks are also used in the production of industrial materials such as ceramics, glass, and abrasives. For example, pumice, a type of igneous rock, is used in the manufacture of abrasives and polishing compounds.

5. Igneous rocks are popular choices for landscaping and decorative purposes due to their diverse colors and textures. Rocks like granite and basalt are often used in landscaping projects such as patios, walkways, and retaining walls.

6. Igneous rock formations like volcanoes, lava flows, and geysers are major attractions for tourists. These geological features draw visitors to areas like national parks and volcanic islands, contributing to the local economy through tourism revenue.

 

SEDIMENTARY ROCK

Sedimentary rocks are formed through the accumulation and consolidation of sediment that has been deposited by wind, water, ice, or chemical precipitation. These rocks account for about 75% of the Earth’s surface and are an important part of the rock cycle.

 

CHARACTERISTICS/PROPERTIES OF SEDIMENTARY ROCKS

Sedimentary rocks play a crucial role in recording Earth’s history, preserving fossils, providing important natural resources, and shaping landscapes around the world. Here are some key characteristics and properties of sedimentary rocks:

1. Formation – Sedimentary rocks are formed through the process of weathering, erosion, transportation, and deposition of sediment. Over time, these loose particles are compacted and cemented together to form solid rocks.

2. Layers – Sedimentary rocks are often characterized by distinct layers or bedding planes that result from the sequential deposition of sediment. These layers can provide valuable information about past environments and geologic history.

3. Composition – Sedimentary rocks are composed of mineral grains, rock fragments, organic matter, and chemical precipitates. The composition of sedimentary rocks can vary widely depending on the source material and the depositional environment.

4. Texture – Sedimentary rocks can have a variety of textures, ranging from fine-grained to coarse-grained. The texture of a sedimentary rock is determined by the size, shape, and sorting of the sediment grains.

5. Fossils –  Sedimentary rocks often contain fossils, which are the preserved remains of plants, animals, or other organisms that lived in the past. Fossils provide important information about ancient life forms and past environments.

6. Porosity and permeability – Sedimentary rocks are often porous and permeable, meaning they contain interconnected spaces (pores) that can hold fluids like water and allow for the movement of fluids through the rock. This property makes sedimentary rocks important reservoirs for groundwater and hydrocarbons.

7. Examples – Common types of sedimentary rocks include sandstone, shale, limestone, conglomerate, and mudstone. Each of these rock types has its own unique characteristics based on the specific type of sediment that formed them.

 

ECONOMICS IMPORTANCE OF SEDIMENTARY ROCKS

The economic importance of sedimentary rocks lies in their role as primary sources of energy, minerals, groundwater, construction materials, and valuable deposits. The extraction and utilization of these resources contribute significantly to local and global economies, supporting various industries, creating jobs, and driving economic development.

Sedimentary rocks have significant economic importance due to their abundance, diversity, and the valuable resources they contain. Some of the key economic benefits of sedimentary rocks include:

1. Sedimentary rocks are the main sources of fossil fuels such as coal, oil, and natural gas. Coal, in particular, is a major energy resource used for electricity generation, industrial processes, and heating. Oil and natural gas extracted from sedimentary rocks are crucial for transportation, heating, electricity generation, and various industrial applications.

2. Sedimentary rocks contain a variety of valuable minerals, including iron ore, bauxite, phosphate, gypsum, and salt. These minerals are essential for manufacturing various products, such as steel, aluminum, fertilizers, building materials, and chemicals.

3. Sedimentary rocks are important reservoirs for storing and supplying groundwater. These rocks often have high porosity and permeability, allowing them to store and transmit water to wells and aquifers for drinking, irrigation, industrial use, and other purposes.

4. Sedimentary rocks such as sandstone, limestone, and shale are commonly used as construction materials for buildings, roads, bridges, monuments, and other infrastructure projects. These rocks are durable, abundant, and aesthetically appealing, making them valuable resources for the construction industry.

5. Sedimentary rocks are often associated with economic deposits of valuable resources, such as placer deposits (gold, diamonds, and other precious metals), evaporite deposits (salt, gypsum, and potash), and petroleum reservoirs. These deposits provide important economic benefits through mining, extraction, and processing activities.

6. Sedimentary rocks can play a role in environmental remediation and pollution control. For example, certain sedimentary rocks like limestone can be used to neutralize acidic mine drainage and treat contaminated water by adsorbing heavy metals and pollutants.

 

METAMORPHIC ROCK

Metamorphic rocks are rocks that have undergone changes in mineral composition, texture, or structure due to heat, pressure, or chemically active fluids without melting. These changes occur in the solid state, typically deep within the Earth’s crust, and result in the formation of new minerals and textures.

 

CHARACTERISTICS/PROPERTIES OF METAMORPHIC ROCKS

The characteristics and properties of metamorphic rocks reflect the complex geological processes that have shaped them and provide valuable information about the conditions under which they formed. These rocks play a crucial role in understanding Earth’s history, tectonic processes, and mineral resources, making them important subjects of study in geology and economic geology. Metamorphic rocks exhibit several characteristics and properties that distinguish them from other rock types:

1. Texture – Metamorphic rocks often have a characteristic texture that reflects the conditions under which they formed. This texture can range from foliated (layered or banded) to non-foliated (uniform or massive) depending on the intensity of pressure and temperature during metamorphism.

2. Mineral composition – Metamorphic rocks are typically composed of minerals that are stable under the high temperatures and pressures of metamorphism. These minerals may include silicates such as quartz, feldspar, mica, and amphibole, as well as minerals like garnet, chlorite, and staurolite that are indicative of specific metamorphic conditions.

3. Foliation – Foliation refers to the alignment of mineral grains or the presence of parallel mineral layers in metamorphic rocks. Foliated rocks, such as schist and gneiss, exhibit distinct banding or layering due to the preferred orientation of elongated minerals like mica or amphibole.

4. Color and appearance – Metamorphic rocks can display a range of colors, textures, and patterns depending on the types and proportions of minerals present. For example, marble is commonly white or gray with distinctive veining, while slate may exhibit a smooth, fine-grained texture and cleavage planes.

5. Hardness and durability – Metamorphic rocks are generally harder and more resistant to weathering compared to sedimentary rocks. Rocks like marble, quartzite, and gneiss are particularly durable and can be polished to a high luster, making them suitable for use as building materials and decorative stones.

6. Metamorphic grade – Metamorphic rocks are classified based on their degree of metamorphism, or metamorphic grade, which is determined by the intensity of heat and pressure they have experienced. Low-grade metamorphic rocks, like slate and phyllite, have undergone mild changes, while high-grade metamorphic rocks, such as gneiss and schist, have undergone more intense metamorphic processes.

 

ECONOMICS IMPORTANCE OF METAMORPHIC ROCKS

Metamorphic rocks may not be as abundant or as economically significant as sedimentary rocks, they still play a valuable role in providing building materials, dimension stone, mineral resources, ore deposits, and geothermal energy sources. The utilization of metamorphic rocks in various industries contributes to economic development, job creation, and resource sustainability.

Metamorphic rocks also have economic importance, although to a lesser extent compared to sedimentary rocks. Some of the key economic benefits of metamorphic rocks include:

1. Metamorphic rocks, such as marble and slate, are highly valued for their aesthetic qualities and durability. Marble is commonly used in construction for countertops, flooring, and decorative elements, while slate is used for roofing tiles, flooring, and decorative purposes. These rocks contribute to the construction industry and provide opportunities for mining and processing activities.

2. Metamorphic rocks like granite, gneiss, and quartzite are important sources of dimension stone, which is used in construction for monuments, sculptures, countertops, and building facades. These rocks are prized for their hardness, durability, and attractive colors, making them valuable resources for architectural and design applications.

3. Metamorphic rocks can host economic deposits of minerals, such as talc, graphite, and garnet. Talc is used in the production of cosmetics, ceramics, paper, and plastics, while graphite is used in batteries, lubricants, and refractories. Garnet is valued for its abrasive properties and is used in sandpaper, waterjet cutting, and other industrial applications.

4. Metamorphic rocks can also host valuable metal ores, including gold, copper, zinc, and lead. These ores are formed through geological processes involving heat and pressure, leading to the concentration of valuable minerals in metamorphic rocks. Mining and extraction activities for these ores contribute to the economy through resource exploration, development, and processing.

5. Metamorphic rocks can act as reservoirs for geothermal energy, where heat from the Earth’s interior is harnessed for electricity generation and heating purposes. High-temperature metamorphic rocks, such as gneiss and schist, can be suitable for geothermal exploration and development, providing renewable energy sources and economic benefits.

 

PROCESSES OF ROCK FORMATION

There are three main processes by which rocks are formed: igneous, sedimentary, and metamorphic. Each process involves different geological processes and conditions that lead to the formation of distinct types of rocks. Here is an overview of each process:

IGNEOUS ROCK FORMATION

1. Igneous rocks are formed from the cooling and solidification of molten rock material, known as magma or lava.

2. Magma is generated within the Earth’s mantle or crust through processes like partial melting of rocks and magma chamber formation.

3. Intrusive igneous rocks form when magma cools and solidifies below the Earth’s surface, resulting in rocks with coarse-grained textures like granite and diorite.

4. Extrusive igneous rocks form when lava erupts onto the Earth’s surface and rapidly cools, resulting in rocks with fine-grained textures like basalt and obsidian.

5. Igneous rocks can also be classified based on their mineral composition, texture, and formation conditions.

 

SEDIMENTARY ROCK FORMATION

1. Sedimentary rocks are formed from the accumulation and compaction of sediment particles derived from pre-existing rocks or biological remains.

2. Weathering and erosion processes break down rocks into sediment particles like sand, silt, and clay, which are transported by water, wind, or ice to depositional environments.

3. Sediments are deposited in layers, or strata, and gradually compacted and cemented together to form sedimentary rocks like sandstone, shale, and limestone.

4. Sedimentary rocks can contain fossils, minerals, and other sedimentary structures that provide clues about the Earth’s history and past environments.

5. Sedimentary rocks are often classified based on their grain size, composition, sedimentary structures, and depositional environments.

 

METAMORPHIC ROCK FORMATION

1. Metamorphic rocks are formed from the alteration of pre-existing rocks (igneous, sedimentary, or other metamorphic rocks) through heat, pressure, and/or chemically active fluids.

2. Metamorphism occurs deep within the Earth’s crust or along tectonic plate boundaries where rocks are subjected to high temperatures and pressures.

3. The process of metamorphism causes changes in mineral composition, texture, and structure, resulting in the formation of metamorphic rocks like marble, slate, and schist.

4. Metamorphic rocks can exhibit foliation, banding, and other distinctive textures that reflect the conditions under which they formed.

5. Metamorphic rocks are classified based on their metamorphic grade, or the intensity of metamorphic processes they have undergone, as well as their mineral composition and texture.

In summary, the processes of igneous, sedimentary, and metamorphic rock formation are interconnected and contribute to the rock cycle, a continuous process of rock formation, transformation, and recycling on Earth’s surface and within the Earth’s interior. These processes play a key role in shaping the Earth’s surface, geological features, and the distribution of valuable mineral resources. These processes of rock formation is how a rock can change from igneous to sedimentary to metamorphic over time.

1. Melted rock or magma is sent to the earth’s surface by a volcano. It cools and forms an igneous rock.

2. Next the weather, or a river, and other events will slowly break up this rock into small pieces of sediment.

3. As sediment builds up and hardens over years, a sedimentary rock is formed.

4. Slowly this sediment rock 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.

 

PRESENTATION

TEACHER’S ACTIVITIES

Teacher,

1. leads student to define rock and differentiate between types of rocks.

2. discuss the processes of rock formation.

3. summarizes the lesson on the board.

 

STUDENT’S ACTIVITIES

Students,

1. define rock and state types of rocks.

2. participate actively in the classroom discussion.

3. copy as the teacher writes.

 

LESSON EVALUATION 

Teacher ask students to:

1. define Rock.

2. mention and discuss the economic importance of different types of rocks.

3. describe the processes of rock formation.