Earth s Rocks DIAGRAM 01: What is the geological timescale? How does the rock cycle work? Section 1: Rock Cycles. Suggested Film.

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Earth s Rocks EARTH SCIENCE GEOLOGY EARTH S ROCKS Section 1: Rock Cycles What is the geological timescale? Rocks can be viewed as records of time.

DIAGRAM 01: The geological timescale is a combination of relative dates and absolute dates.

another. Absolute dates provide a numerical age for the rocks using techniques such as radiometric dating.

1 Earth s Rocks EARTH SCIENCE GEOLOGY EARTH S ROCKS Section 1: Rock Cycles What is the geological timescale? Rocks can be viewed as records of time. The geological timescale represents the relationship between past events, and describes the timing of these events in relation to each other. DIAGRAM 01: The geological timescale is a combination of relative dates and absolute dates. Relative dates describe the order in which the rocks were created, and these are based largely on changes in the types of fossils in the rock or the structural relationship between one rock layer and another. Absolute dates provide a numerical age for the rocks using techniques such as radiometric dating. The timescale is split into different units, based on major geological events, and these different units can be correlated across continents based on the fossils they contain. Suggested Film - Rock Cycles How does the rock cycle work? Magma that reaches the Earth s surface is called lava Over geological time the three different types of rock are recycled. Igneous rocks are created within the Earth, or erupted from volcanoes, and come into contact with the atmosphere where they are broken down by weathering. The products of this weathering are eroded and deposited elsewhere, they are buried and then compacted to form sedimentary rocks. These buried rocks are subjected to high pressures and temperatures, and can become deformed and form metamorphic rocks. The metamorphic rock within the Earth can also melt to become magma, which is the basis of igneous rocks. - Rock Cycles - How Hot Is the Earth s Core? 1

DIAGRAM 02: Mountains are formed when the Earth s crust is pushed upwards What is the difference between rocks and minerals? Rocks and minerals are both formed by geological processes.

Minerals such as gold (Au) are composed of a single element, whereas minerals such as quartz (SiO 2 ) or feldspar are compounds of elements.

They can instead be classifi ed according to their bulk composition, which is the overall percentage of different elements or minerals in the rock.

2 DIAGRAM 02: Mountains are formed when the Earth s crust is pushed upwards What is the difference between rocks and minerals? Rocks and minerals are both formed by geological processes. Minerals consist of chemical elements or compounds, and are generally classifi ed by their chemical structure and specifi c physical properties. Minerals such as gold (Au) are composed of a single element, whereas minerals such as quartz (SiO 2 ) or feldspar are compounds of elements. Rocks are made up of one or more minerals and do not need to have a specifi c chemical composition. They can instead be classifi ed according to their bulk composition, which is the overall percentage of different elements or minerals in the rock. Rocks can therefore have the same bulk composition, but can contain a different collection of minerals depending on the conditions under which they were formed. - Rock Types - Earthly Treasures: Precious Gemstones - Earthly Treasures: Diamonds Extension Question Amethyst is a gemstone mineral Q1. What are gemstones? Gemstones are generally minerals, such as diamond, ruby or sapphire, which have often been cut and polished to reveal their beauty. However, some rocks are considered to be gemstones too, such as turquoise or lapis lazuli. Some are organic materials, such as pearl or amber. Perhaps the defi ning feature of a gemstone is that is has been reworked from a naturally occurring material to turn it into a precious or semiprecious stone. Local geological conditions are important; it is the relative rarity of these minerals and the diffi culty involved in mining them that makes them valuable. 2

A scale of mineral hardness called Moh s scale is used; the scale ranges from talc at the softest end to diamond at the hardest end. Section 2: Rock Types What is igneous rock?

3 Extension Question Q2. How do we compare the hardness of a mineral? There are several ways to determine the hardness of a mineral, but the most common way is to compare it to the hardness of other minerals in terms of its ability to scratch them. A scale of mineral hardness called Moh s scale is used; the scale ranges from talc at the softest end to diamond at the hardest end. Section 2: Rock Types What is igneous rock? Igneous rocks form from magma, which consists of liquid rock material with gas and crystals. Magma is formed deep within the Earth from the melting of preexisting rocks by geothermal heat, and can solidify within the Earth to form an intrusive igneous rock, or can be erupted at the surface as lava to form an extrusive igneous rock. These smooth granite pebbles are an example of igneous rock - Rock Types Igneous rocks are classifi ed by their composition and their texture. When magma cools slowly, as for intrusive rocks, the minerals have time to form large crystals, and the resulting rock is coarse-grained like granite. When lava is exposed to the air it cools rapidly and forms fi ne-grained rocks like basalt. These rocks are found in locations such as Iceland and the Isle of Skye, Scotland. What are the characteristics of sedimentary rocks? Sedimentary rocks are formed as a result of processes acting at the Earth s surface and are related to the Water Cycle. They can be formed in many different environments, by the action of water, wind, gravity or ice. Sedimentary rocks can form from fragments of preexisting rock which has been weathered and eroded; these are known as clastic rocks. Sedimentary rocks, such as limestone and chalk, also form from the accumulation of organisms or the precipitation of minerals from solution that were once sea fl oor deposits. Sedimentary rocks are deposited in layers, producing a structure known as bedding. They can also preserve evidence of past environmental conditions in the form of fossils or sedimentary structures, like ripple marks. Extension Questions Q3. What is a fossil? A fossil is evidence of life in the geological past preserved in sedimentary rock layers. It can be the remains of plants and animals, or can even be the preserved traces of animal activity known as trace fossils. There are clear layers in this sedimentary sandstone rock Q4. How do fossils form? Fossils can be preserved remains of the parts of organisms, such as shells or bones, or can occur where parts of the organism are replaced by minerals as it is buried. Sometimes the organism dissolves and its space is fi lled with sediment, forming a cast, and sometimes features such as tracks and burrows can be fi lled with a different type of sediment to form a trace fossil. 3

How are metamorphic rocks formed? When rocks are subjected to high pressures and temperatures, the texture and composition of the rock can be drastically altered to form metamorphic rock.

4 How are metamorphic rocks formed? When rocks are subjected to high pressures and temperatures, the texture and composition of the rock can be drastically altered to form metamorphic rock. Any type of rock can change into metamorphic rock. The increase in temperature or pressure occurs for a number of reasons. Burial of rock deep within the Earth subjects the rock to high temperatures and pressure from the rocks above, while horizontal pressure from the collision of tectonic plates can deform the rocks in a whole region. The heat from intrusive igneous rocks can subject the surrounding rock to high temperatures and change their mineral composition. This type of change is known as contact metamorphism. - Rock Types - Earthly Treasures: Diamond Marble is an example of a metamorphic rock Extension Questions Q5. How can you tell what type of rock you are holding? Rocks are classifi ed by their composition, in terms of the minerals or the chemical elements they contain, the texture of the minerals within the rock and the processes that formed the rock. To classify the rock by composition it may be necessary to look at the rock under a microscope or perform chemical analysis on it. Texture can often be seen by the naked eye and provide clues about how the rock formed. For example, metamorphic rocks are often banded and folded with certain minerals aligned along the folds. Sedimentary rocks can contain particles, or clasts, with a distinct shape which indicates where they were deposited. It can still prove diffi cult to distinguish between the many rock types. Q6. How does landscape differ between major rock types? Although the Earth has a variety of different landscapes, all of the continents are generally composed of the same landscape features. The centers of continents are composed of very old (igneous and metamorphic) rocks known as basement rock. The top of this region is known as the shield, and is often a large and relatively fl at area. The shield is often covered by fl at or gently sloping layers of sedimentary rock and river drainage produces rolling hills. In any area, the landscape is determined by how resistant the different sedimentary rocks are to erosion. They can be folded in mountain belts (e.g. the Alps), formed above a subduction zone, or where two continents collide. If the folded sedimentary rocks are eroded, the landscape is determined by the stronger igneous and metamorphic rocks underneath. The more resistant igneous rocks can form mountain ranges, while the surrounding rocks are eroded to form lowland areas. 4

Section 3: Rocks and Man What is rock used for in everyday life? Rocks are used in their bulk form and are processed to extract the minerals they contain.

5 Section 3: Rocks and Man What is rock used for in everyday life? Rocks are used in their bulk form and are processed to extract the minerals they contain. Rocks are therefore used in a surprising number of ways in our everyday lives. Rocks such as granite, limestone and sandstone can be used for construction, and crushed rocks can be used to build roads and other infrastructure. Coal is mined and used to generate a large percentage of our electricity and oil is extracted from rocks and processed for use as fuel, powering our transport systems. The smoothness of marble makes it a popular choice for sculptures The metals extracted from rocks are used to manufacture things as diverse as computers, airplanes, drinks cans, and the plumbing and wiring in our homes. The plates that we eat our food from are often made of clay, which is a weathering product of rocks, and the salt we put on our food is also derived from rocks. There are also rare earth elements that are vital to the electronic components in our cell phones. The supply of these products will become increasingly important in the future. - Structure of the Earth - Earthly Treasures: Precious Gemstones - Earthly Treasures: Gold Suggested Activity - Ask the students to identify the different times in a typical day when rocks are needed. Use some of the examples mentioned in the question above as a starting point. Extension Questions Q7. How are diamonds formed? Diamonds are composed of carbon that comes from the melting of preexisting rocks. Natural diamonds form at high pressures and temperatures that can only be found deep within the Earth, especially where the continental crust is very thick, before being brought near to the surface in volcanic eruptions. Diamond extraction is diffi cult and recently extra measures have been introduced to ensure that the miners are treated fairly and can work safely. Q8. Why is gold so precious? The chemical and physical properties of gold make it particularly useful and desirable. It is malleable, which means it can be shaped easily, it is resistant to chemical reactions, and is also a good conductor of electricity. Gold is therefore very durable and can be used in many ways. 5

While surface limestone features may be minimal, underground features, such as caves and drainage systems, are common.

6 What are the features of limestone? Limestone is a sedimentary rock, which makes up around 10% of the Earth s land surface. It has regular cracks caused during its formation, and is permeable, which means that water moves through it easily. While surface limestone features may be minimal, underground features, such as caves and drainage systems, are common. The Yorkshire Dales have a range of large caves formed in carboniferous limestone, including Gaping Gill, which is over 100m deep. The dissolved rock is re-deposited in some caves to form stalactites and stalagmites, Limestone is shaped into distinctive features as it is worn down by water and weathering The term karst is used to describe the topography of limestone landscapes. Rainwater is weakly acidic, and this dissolves the rock over time. The ground tends to be undulating where weaker areas of limestone have been dissolved more rapidly. The varying color of limestone makes it a popular building material, although erosion from rainwater can become a big problem. - Limestone: Features - Limestone: Formation, Forms and Uses What are the impacts of quarrying? The extraction of rocks and minerals has an obvious impact on the environment. Mining and quarrying involves removing large quantities of rocks (overburden) to reach the valuable ores and mineral seams at greater depth. This process may involve blasting with large machinery and huge vehicles. Dust can spread some distance from the quarry, and there may be increased traffic on local roads as large vehicles take away the rock. Associated industries can also develop, for example cement factories are built close to limestone quarries to create jobs. Many quarries are eventually restored, with holes being flooded lakes, or vertical surfaces used for climbing. One of the most famous restoration projects led to the building of the Eden Project in Cornwall. - Quarrying: the Impacts - Quarrying: Managing Negative Impacts This pumice is an igneous rock, evident from the many tiny holes present 6

7 Quizzes Rock Types Basic Advanced Which is not a main type of rock? A igneous B sedimentary C continental D metamorphic Plant and animal remains found in sedimentary rock are known as A debris B detritus C fossils D diamonds Rock produced from cooling magma is A metamorphic B igneous C bionic D magmorphic Rocks which have changed through excessive heat and pressure are said to be A metamorphic B thermophilic C barometric D sedimentary Which of these does not affect rocks appearance and properties? A size of grains B type of minerals C how the rocks were formed D which hemisphere the rocks originated from Sandstone is made up of round grains with tiny gaps between them which makes it A soft and porous B hard and impermeable C soft and impermeable D extremely hard Igneous rock at the surface is known as A intrusive rock B invasive rock C extrusive rock D extensive rock After undergoing a change under heat and pressure, sandstone becomes A diamond B quartz C slate D shale 7

8 Rock Cycles Basic Advanced The breaking down of rocks and the creation of new ones is called A rock regeneration B rock renovation C rock cycle D rock system Approximately how old is the oldest rock ever found on Earth? A 4 million years old B 4 billion years old C 400,000 years old D 40,000 years old Rocks that have changed under heat and pressure are best termed A igneous rocks B metamorphic rocks C lava D magma Under intense heat and pressure, limestone rock can change to A marble B chalk C slate D diamond What does cooling magma form? A igneous rocks B metamorphic rocks C sedimentary rock D fossils Rising magma pushing rocks up on the surface is a process known as A faulting B uplift C elevation D rebound 8

9 Answers Rock Types Basic Advanced Which is not a main type of rock? A igneous B sedimentary C continental D metamorphic Plant and animal remains found in sedimentary rock are known as A debris B detritus C fossils D diamonds Rock produced from cooling magma is A metamorphic B igneous C bionic D magmorphic Rocks which have changed through excessive heat and pressure are said to be A metamorphic B thermophilic C barometric D sedimentary Which of these does not affect rocks appearance and properties? A size of grains B type of minerals C how the rocks were formed D which hemisphere the rocks originated from Sandstone is made up of round grains with tiny gaps between them which makes it A soft and porous B hard and impermeable C soft and impermeable D extremely hard Igneous rock at the surface is known as A intrusive rock B invasive rock C extrusive rock D extensive rock After undergoing a change under heat and pressure, sandstone becomes A diamond B quartz C slate D shale 9

10 Rock Cycles Basic Advanced The breaking down of rocks and the creation of new ones is called A rock regeneration B rock renovation C rock cycle D rock system Approximately how old is the oldest rock ever found on Earth? A 4 million years old B 4 billion years old C 400,000 years old D 40,000 years old Rocks that have changed under heat and pressure are best termed A igneous rocks B metamorphic rocks C lava D magma Under intense heat and pressure, limestone rock can change to A marble B chalk C slate D diamond What does cooling magma form? A igneous rocks B metamorphic rocks C sedimentary rock D fossils Rising magma pushing rocks up on the surface is a process known as A faulting B uplift C elevation D rebound 10

Rocks & Minerals. Lesson 1 Properties of Minerals. What is a mineral? What is a mineral?

Rocks & Minerals. Lesson 1 Properties of Minerals. What is a mineral? What is a mineral? Rocks & Minerals What is a mineral? A mineral must have 5 specific characteristics to be considered a mineral a. b. c. d. e. Naturally occurring - formed by natural processes. Solid - must have a definite