Chapter 1 The Changing Earth

Approximately 75% of the earth's surface is covered by water. This includes oceans, seas, lakes, rivers, and other bodies of water. The large percentage of water on earth is essential for supporting various ecosystems and sustaining life. It plays a crucial role in regulating climate, providing habitats for marine life, and influencing weather patterns.

As you travel deeper into the earth, the temperature increases. This is because the earth's interior is heated by the decay of radioactive elements and residual heat from its formation. The increase in temperature with depth is known as the geothermal gradient. The deeper you go, the more heat is trapped and the higher the temperature becomes. This is why deep mines and boreholes can become extremely hot.

The correct answer is "the bottom layers of rock." This is because the oldest fossils are typically found in the lower layers of rock, as new layers of sediment accumulate on top of older ones over time. As a result, the fossils that are found deeper in the Earth's crust are generally older than those found closer to the surface.

The water that covers the earth is called the hydrosphere. The term "hydrosphere" refers to all the water on Earth, including that found in oceans, seas, lakes, rivers, glaciers, and even underground. It plays a crucial role in supporting life on our planet, regulating climate, and shaping the Earth's surface through various processes like erosion and weathering. The lithosphere, on the other hand, refers to the solid outer layer of the Earth, while the atmosphere refers to the layer of gases surrounding the planet.

The correct answer is core. The core refers to the innermost layer of the Earth, located at the center. It is primarily composed of iron and nickel and is divided into two parts: the outer core and the inner core. The outer core is liquid, while the inner core is solid. The core plays a crucial role in generating Earth's magnetic field and is responsible for the intense heat and pressure found in the Earth's interior.

The rigid outer shell of the earth that includes the crust and the solid part of the mantle is called the lithosphere. The lithosphere consists of the solid, rocky material that makes up the earth's surface, including the continents and oceanic crust. It is divided into several tectonic plates that float on the semi-fluid asthenosphere beneath them. The hydrosphere refers to all the water on earth, including oceans, lakes, rivers, and groundwater. The atmosphere is the layer of gases that surround the earth.

A mineral is a natural, non-living solid that has a definite chemical structure. It is formed through geological processes and has a specific composition of atoms arranged in a repeating pattern. Minerals can be found in rocks and are classified based on their physical and chemical properties. They are essential in various industries and have a wide range of uses, including in construction, jewelry, and technology.

The correct answer is atmosphere. The question asks for the layers of gases that surround the earth, and the atmosphere is the correct term for this. The lithosphere refers to the solid outer part of the earth, while the hydrosphere refers to all the water on earth's surface. Therefore, the atmosphere is the most appropriate term to describe the layers of gases surrounding the earth.

The rock cycle is a process through which rocks can change form. It involves the transformation of rocks from one type to another over time, due to various geological processes such as weathering, erosion, melting, and cooling. This cycle includes three main rock types: igneous, sedimentary, and metamorphic. Igneous rocks are formed from the cooling and solidification of molten magma, sedimentary rocks are formed from the accumulation and compression of sediment particles, and metamorphic rocks are formed when existing rocks undergo intense heat and pressure, causing them to change their structure and composition. The rock cycle is a continuous and dynamic process that occurs over millions of years.

Physical weathering refers to the process by which rocks are broken apart into smaller pieces without altering their composition. This can occur through various mechanisms such as freeze-thaw cycles, abrasion from wind or water, and thermal expansion and contraction. Despite the physical breakdown, the rocks retain their original mineral composition and chemical properties. In contrast, chemical weathering involves the alteration of the substances that rocks are made of, leading to changes in their composition.

Rocks formed when layers of sediment are pressed or cemented together at the bottom of a body of water are called sedimentary rock. Sedimentary rocks are formed through the process of sedimentation, where sediments such as sand, mud, and organic material accumulate over time and are compacted and hardened into rock. This process commonly occurs in bodies of water such as oceans, lakes, and rivers. Sedimentary rocks often contain fossils and provide important clues about Earth's history and past environments.

The correct answer is "at the speed your fingernails grow." This statement suggests that the movement of the earth's plates is extremely slow. Comparing it to the speed at which fingernails grow implies that the movement is almost imperceptible or negligible.

The movement of the earth's plates is primarily caused by the heat generated from the core. This heat causes the mantle, which is the layer above the core, to become hot and less dense. As a result, the hot mantle rises towards the surface, creating convection currents. These convection currents push against the crust, causing the plates to move. Earthquakes are a result of the movement and interaction of these plates, rather than the direct cause of plate movement.

Erosion is the process of wearing away the Earth's surface through the movement of soil, rocks, or sediment. One of the main causes of erosion is the force of flowing water, such as rivers, streams, or even heavy rainfall. As water moves over the land, it can pick up and carry away soil particles, gradually eroding the land. While plants can help reduce erosion by stabilizing the soil with their roots, they are not the main cause of erosion. Pollution, although it can have negative effects on the environment, is not directly related to erosion.

The question asks for the rigid outer shell of the Earth, and the correct answer is the lithosphere. The lithosphere is the uppermost layer of the Earth's crust and the rigid part of the mantle. It is composed of both the crust and a portion of the upper mantle, and it is broken into tectonic plates that float on the semi-fluid asthenosphere underneath. The lithosphere is responsible for the formation of continents, ocean basins, and the movement of tectonic plates.

Plate tectonics is the theory that explains how the Earth's surface is divided into several large and small plates that are constantly moving. These plates interact with each other at their boundaries, causing various geological phenomena such as earthquakes, volcanic eruptions, and the formation of mountains. The theory of plate tectonics provides a comprehensive explanation for the distribution of continents, the formation of ocean basins, and the occurrence of seismic and volcanic activities around the world. It has been widely accepted by the scientific community and has revolutionized our understanding of the Earth's dynamic nature.

The layer that is made up of solid rock and soil is the crust. The crust is the outermost layer of the Earth and is composed of a variety of rocks and minerals. It is the thinnest layer and is divided into two types: oceanic crust, which is found beneath the oceans, and continental crust, which is found beneath the continents. The crust is where we find the Earth's surface and where all life exists.

When two tectonic plates strain against each other and then suddenly move, it creates a release of energy in the Earth's crust, resulting in seismic waves. These seismic waves cause vibrations and shaking of the ground, which we commonly refer to as earthquakes. Therefore, earthquakes happen when two plates strain against each other and then move suddenly.

The evidence that suggests the continents were once connected as a "supercontinent" that has moved apart over time includes the presence of ancient mountains, the location of coal deposits, fossil discoveries, and glacial deposits. Ancient mountains, such as the Appalachian Mountains in North America and the Caledonian Mountains in Europe, have similar rock formations and ages, indicating that they were once connected. The distribution of coal deposits across different continents also supports the idea of a supercontinent, as coal forms in swampy environments that were likely connected in the past. Fossil discoveries of similar species on different continents and the presence of glacial deposits in areas that are now warm also indicate that the continents were once connected.

The core refers to the innermost layer of the Earth, and it is composed of iron and nickel. This is supported by scientific evidence and theories, such as the study of seismic waves and the Earth's magnetic field. The iron and nickel in the core are believed to be in a molten state due to the extremely high temperatures and pressures. This composition of the core is crucial in understanding the Earth's internal structure and dynamics.

Water freezing in a crack in a rock can cause physical weathering because when the water freezes, it expands and exerts pressure on the rock. This pressure can cause the crack to widen and eventually lead to the rock breaking apart. This process is known as frost wedging and is a common form of physical weathering in cold climates.

Weathering is the process that breaks down and changes rock. It involves the physical, chemical, and biological processes that wear down rocks and minerals over time. This can occur through factors such as temperature changes, water, wind, and the actions of plants and animals. Weathering can cause rocks to break apart and change in composition, leading to the formation of soil and sediment. Erosion, on the other hand, refers to the movement and transportation of weathered materials, while deposition is the process of depositing or laying down sediment in a new location.

Metamorphic rocks are formed when pre-existing rocks, either sedimentary, igneous, or even other metamorphic rocks, undergo significant changes due to intense heat and pressure. These changes can cause the minerals within the rocks to recrystallize, resulting in a new rock with different physical and chemical properties. Therefore, metamorphic rock is the correct answer as it accurately describes the process of rocks being changed by heat and pressure.

The middle layer of the earth is the mantle. The earth is divided into three main layers: the crust, mantle, and core. The mantle is located between the crust and the core. It is a thick layer of hot, solid rock that surrounds the core. The mantle plays a crucial role in the movement of tectonic plates and the convection currents that drive plate tectonics. It is also responsible for the release of volcanic gases and the formation of magma.

Volcanoes and earthquakes usually occur at plate boundaries because these are the areas where tectonic plates interact and create intense geological activity. At plate boundaries, plates can collide, separate, or slide past each other, causing the release of energy that leads to earthquakes and the formation of volcanoes. These boundaries can be found in various forms, such as convergent boundaries where plates collide, divergent boundaries where plates separate, and transform boundaries where plates slide past each other. The interaction between tectonic plates at these boundaries is responsible for the majority of volcanic and seismic activity on Earth.

The correct answer is "chemical physical, physical chemical". This answer suggests that there are two types of weathering: chemical weathering and physical weathering. Both types play a role in the breakdown and alteration of rocks and minerals. Chemical weathering involves the chemical reactions that cause rocks to decompose and change composition, while physical weathering refers to the mechanical processes that physically break down rocks into smaller fragments. The order of the terms in the answer does not matter as both combinations convey the same meaning.

Erosion can have multiple impacts on the environment. It can carry away rich farmland, leading to a loss of fertile soil and decreased agricultural productivity. Additionally, erosion can change the shoreline by wearing away coastal land and depositing sediment in new areas. Finally, erosion can cause buildings to collapse, especially if the foundation is weakened by the removal of supporting soil. Therefore, all of the given options are correct as erosion can indeed carry away rich farmland, change the shoreline, and cause buildings to collapse.

The lithosphere is the rigid outer layer of the Earth, consisting of the crust and uppermost part of the mantle. It is primarily composed of rock and minerals, which form the solid foundation of the Earth's surface. Water and ice are found in the hydrosphere and cryosphere, while lava and magma are part of the Earth's molten interior and are found in the asthenosphere and lower mantle. Therefore, the correct answer is rock and minerals.

Deposition refers to the process of dropping or laying down eroded materials, such as sediment or soil, in a new location. It occurs when the transporting agent, like water or wind, loses energy and can no longer carry the materials. The particles settle and accumulate, forming layers of sediment over time. This process is distinct from weathering, which involves the breakdown of rocks and minerals, and erosion, which involves the transportation of these materials from one place to another. Therefore, the correct answer is deposition.

Heat and pressure can cause the atoms in a mineral to rearrange themselves, leading to the formation of crystals. These crystals can vary in size depending on the specific conditions of heat and pressure. The increase in temperature and pressure can disrupt the original arrangement of atoms, allowing them to bond together in a new pattern and form crystals of different sizes. This process, known as recrystallization, is a common phenomenon in the Earth's crust and is responsible for the formation of various types of minerals with distinct crystal structures.

Iron rusting is an example of chemical weathering because it involves a chemical reaction between iron, oxygen, and water. This reaction leads to the formation of iron oxide, commonly known as rust. Over time, the rust weakens the iron, causing it to break down and deteriorate. This process is a prime example of how chemical reactions can cause the weathering and degradation of materials.

Limestone is an example of a sedimentary rock because it is formed from the accumulation and compaction of sediment, such as shells and coral fragments, over time. Sedimentary rocks are formed through the processes of weathering, erosion, deposition, and lithification, where sediments are compacted and cemented together. Limestone is commonly found in areas where there were once shallow seas or lakes, making it a prime example of a sedimentary rock. Marble, granite, and pumice are not sedimentary rocks but instead belong to other rock types such as metamorphic and igneous.

The Mohs Scale is a scale used to measure the hardness of minerals. Hardness refers to a mineral's ability to resist being scratched or damaged. The scale ranges from 1 (softest) to 10 (hardest), with diamond being the hardest mineral. Therefore, the correct answer is hardness.

Rocks formed when melted rock from deep in the earth cools are called igneous rock. Igneous rocks are formed when molten rock, or magma, cools and solidifies. This process can occur either underground or on the earth's surface. As the magma cools, it crystallizes and solidifies, forming igneous rocks. These rocks can have a variety of textures and compositions, depending on factors such as the cooling rate and the mineral content of the magma. Examples of igneous rocks include granite, basalt, and obsidian.

Fossils are usually found in sedimentary rock because this type of rock is formed from layers of sediment that accumulate over time. As organisms die and their remains settle on the ocean floor or in lakes, they become buried in sediment. Over millions of years, the weight of the sediment compacts and hardens, preserving the fossils within. Sedimentary rock also often contains fossils because it is formed in environments where organic material is more likely to be preserved, such as riverbeds, deltas, and ocean basins. In contrast, metamorphic and igneous rocks are formed through processes that involve high heat and pressure, which typically destroy any fossils present.

The materials in the inner core are solid, while the materials in the outer core are liquid. This is because the inner core is under extreme pressure, which causes the materials to be compressed into a solid state. On the other hand, the outer core is less pressurized, allowing the materials to remain in a liquid state.

When two plates collide, immense pressure is exerted on the crust, causing it to buckle and fold. This process, known as orogeny, leads to the formation of mountains. The collision forces the rocks to compress and uplift, creating large-scale geological structures such as mountain ranges. The intense pressure and movement also result in earthquakes, and in some cases, the collision can cause volcanic activity. However, the primary outcome of plate collision is the formation of mountains.

Deposition is the process by which sediment is deposited or added to a landform. Deltas are formed when sediment is deposited at the mouth of a river, dunes are formed when wind deposits sand, and beaches are formed when waves deposit sand along the shoreline. However, deposition does not contribute to the formation of mountains. Mountains are typically formed through tectonic processes such as uplift and folding, or through volcanic activity. Therefore, the correct answer is mountains.

When two plates are pulled apart, the process is known as seafloor spreading. This occurs at divergent plate boundaries, where molten rock from the mantle rises to the surface and creates new crust. As the molten rock cools and solidifies, it forms new crust, adding to the existing plates. This process is responsible for the formation of new oceanic crust and the widening of the seafloor. Therefore, the correct answer is that new crust forms.

Granite is an example of an igneous rock because it is formed from the cooling and solidification of molten magma deep within the Earth's crust. It is composed of minerals such as quartz, feldspar, and mica, which give it a coarse-grained texture. Granite is commonly found in continental crust and is widely used in construction and as a decorative stone. Sandstone, limestone, and marble, on the other hand, are sedimentary or metamorphic rocks, formed through different processes.

The outer core of the Earth is made up of liquid iron and nickel, while the inner core is solid. This is supported by scientific evidence and theories about the Earth's structure. The outer core is believed to be in a liquid state due to the high temperatures and pressures present in that region. However, the inner core, despite even higher temperatures, is solid due to the immense pressure exerted on it by the surrounding layers. This explanation aligns with our current understanding of the Earth's core composition.

The earth's surface is broken into about 20 plates. These plates are called tectonic plates and they float on the semi-fluid asthenosphere beneath them. The movement of these plates is responsible for various geological phenomena such as earthquakes, volcanic activity, and the formation of mountains. The theory explaining this movement is called plate tectonics, which states that the earth's lithosphere is divided into several rigid plates that constantly interact with each other.

Erosion refers to the process of moving weathered rock and soil from one place to another. It is caused by natural agents such as water, wind, or ice, which gradually wear away and transport the loose particles. This movement can result in the formation of new landforms and the reshaping of the Earth's surface. Weathering, on the other hand, refers to the breakdown and decay of rocks and minerals in situ, without any movement. Deposition is the process of laying down sediments or particles that have been eroded and transported by erosion.

The crust is thinner under the oceans and thicker under the continents. This is because the oceanic crust is made up of denser basaltic rocks, which are thinner and more compact. In contrast, the continental crust is composed of less dense granitic rocks, which are thicker and less compact. The variation in crust thickness is due to the differences in the composition and density of the rocks that make up the oceanic and continental crusts.

The atmosphere is primarily composed of nitrogen, which makes up about 78% of the Earth's atmosphere. Oxygen, although important for supporting life, only makes up about 21% of the atmosphere. Water vapor and carbon dioxide are present in much smaller amounts compared to nitrogen and oxygen.

Marble is an example of a metamorphic rock because it is formed from the transformation of limestone, which is a sedimentary rock, through heat and pressure over time. This process causes the minerals in the limestone to recrystallize, resulting in the formation of marble. Therefore, marble is a clear example of a metamorphic rock.

When one plate is pushed under another plate, it creates a subduction zone. In this zone, the subducting plate sinks into the mantle, causing intense heat and pressure. This leads to the melting of the subducting plate, which in turn creates magma. As the magma rises to the surface, it forms volcanoes. Therefore, when one plate is pushed under another, volcanoes occur.