Volcanoes - Chapter 9

Magma that reaches Earth's surface is known as lava. When molten rock, or magma, escapes from beneath the Earth's crust and flows onto the surface, it is called lava. Lava can be found in volcanic eruptions, where it can flow slowly or explosively, and it eventually cools and solidifies to form igneous rock. Lava is a vital component in the formation of volcanic landforms and plays a significant role in shaping the Earth's surface.

All of the options listed (Shield, Composite, and Cinder cone) are types of volcanoes. A shield volcano is a broad, gently sloping volcano formed by thin, runny lava that spreads over a large area. A composite volcano, also known as a stratovolcano, is a tall, steep-sided volcano formed by alternating layers of lava and ash. A cinder cone volcano is a small, steep-sided volcano formed by explosive eruptions of cinders and other volcanic debris. Therefore, the correct answer is "All of the above" as all three options are types of volcanoes.

Iceland is the correct answer because it is the only option where a mid-ocean ridge rises above sea level. Iceland is located on the Mid-Atlantic Ridge, which is a divergent boundary between the North American and Eurasian tectonic plates. This ridge is unique because it extends above the surface of the ocean, creating volcanic activity and geothermal features on the island. The other options, France, Japan, and Jamaica, do not have mid-ocean ridges that rise above sea level.

Viscosity refers to a substance's resistance to flow. It is a measure of the internal friction within a fluid, determining how easily it can flow or how resistant it is to deformation. Viscosity is influenced by factors such as temperature, pressure, and molecular structure. Liquids with high viscosity, like honey or syrup, flow slowly and have a thick consistency, while liquids with low viscosity, like water, flow easily and have a thin consistency.

Olympus Mons is the largest known volcano in the solar system. This volcano is located on Mars and is about 13.6 miles (22 kilometers) high, making it nearly three times the height of Mount Everest. Olympus Mons is also about 370 miles (600 kilometers) in diameter, which is roughly equivalent to the size of the state of Arizona. Its massive size is due to the fact that Mars does not have tectonic plate movement like Earth, allowing the volcano to continuously erupt and build up over time.

A volcano is an opening in Earth's crust through which molten rock, gases, and ash erupt. It is also the landform that develops around the opening.

Crater Lake is a caldera because it was formed by the collapse of a volcano after a massive eruption. The eruption caused the volcano to empty its magma chamber, resulting in the collapse of the volcano's summit. This collapse created a large, circular depression that eventually filled with water, forming Crater Lake. Mauna Loa, Mount Shasta, and Capulin are not calderas. Mauna Loa is a shield volcano, Mount Shasta is a stratovolcano, and Capulin is a cinder cone volcano.

A lahar is a fast-moving mudflow that occurs when hot ash from a volcanic eruption mixes with snow and ice on the mountain. This mixture creates a fluid-like mass that can quickly flow down the slopes of the volcano, potentially causing significant destruction and posing a threat to nearby communities. Lahars are often triggered by volcanic activity, such as eruptions or the melting of glaciers due to volcanic heat, and can carry large amounts of debris, rocks, and water.

A large crater-shaped basin is known as a caldera. A caldera is formed when a volcano collapses or erupts, causing the ground to sink and form a large circular or elliptical depression. This depression is usually several kilometers in diameter and can be filled with water or volcanic material. Calderas are typically formed after a volcanic eruption expels a large amount of magma, causing the volcano to collapse inward. They are often characterized by steep walls and may contain hot springs or geothermal activity.

Magma tends to rise to the surface because it is less dense than the surrounding materials. This is due to the high temperature and the presence of gases within the magma. The buoyancy force caused by the density difference causes the magma to move upwards towards the Earth's surface. As it rises, it can eventually erupt as a volcano or form intrusions such as dikes or sills.

Scientists rely on photographs to understand the history of volcanic activity on the moon because photographs provide visual evidence of past volcanic eruptions and lava flows. By studying the size, shape, and distribution of volcanic features captured in photographs, scientists can determine the age and duration of volcanic activity, as well as the types of volcanic processes that occurred. Additionally, photographs can reveal the presence of specific volcanic materials and help identify potential future volcanic hazards.

The eruption of Mount Vesuvius in A.D. 79 caused a pyroclastic flow, which is a fast-moving cloud of hot gas, ash, and volcanic materials. This flow buried the Roman city of Pompeii under layers of pumice and ash. Pompeii was a thriving city at the time, and the eruption preserved the city and its inhabitants in remarkable detail, providing valuable insights into Roman life and culture.

Crater Lake is a caldera formed by the collapse of a volcano after a massive eruption. It is located in Oregon.

Basaltic lava has a low viscosity, meaning it is less resistant to flow. This allows it to travel long distances before solidifying. The low viscosity is due to the low silica content in basaltic lava, which makes it more fluid compared to other types of lava. As a result, basaltic lava can flow for several kilometers before cooling and hardening into solid rock.

Lapilli are intermediate sized pieces of pyroclastic material. They are typically between 2 and 64 millimeters in diameter and are formed during volcanic eruptions. Lapilli are larger than ash particles but smaller than blocks and bombs. They are often rounded or angular in shape and can be composed of various materials such as volcanic glass, pumice, or rock fragments. Lapilli can be ejected into the air during explosive eruptions and can also accumulate on the ground, forming layers of volcanic deposits.

A dense, superheated cloud of gases and pyroclastic material that moves rapidly downhill from an erupting volcano is called a pyroclastic flow. This phenomenon occurs when volcanic ash, rocks, and gas mix together and flow down the volcano's slopes due to gravity. Pyroclastic flows are extremely dangerous and can reach speeds of up to 700 km/h, causing widespread destruction and posing a significant threat to human life and infrastructure.

A volcanic eruption occurs when magma rises to the surface. This happens when the pressure exerted by the magma becomes greater than the confining pressure of the surrounding rocks, causing the magma to push its way up towards the surface. As the magma rises, it may encounter cracks or openings in the Earth's surface, allowing it to escape and erupt onto the surface as lava, ash, and gases.

The amount of silica in magma determines its viscosity. Silica-rich magma has a higher viscosity, meaning it is more resistant to flow. This affects the rate at which magma rises to the surface. Magma with high silica content tends to be more explosive as gases cannot easily escape. On the other hand, magma with low silica content has low viscosity and can flow more easily, resulting in less explosive eruptions. Therefore, the amount of silica in magma is a crucial factor in determining its characteristics and the rate at which it rises.

Explosive eruptions are typically caused by the release of trapped gases in magma. As magma rises to the surface, the decrease in pressure allows these gases, such as water vapor, carbon dioxide, and sulfur dioxide, to expand and escape. The rapid expansion of these gases can lead to explosive eruptions, as the force of the escaping gases can fragment the magma and propel it into the air. Therefore, the presence of trapped gases in magma is a common characteristic of more explosive volcanic eruptions.

The broad base of a shield volcano is able to support a mountain with enormous height. Shield volcanoes have gentle slopes and are formed by the accumulation of lava flows, which spread out and create a wide base. This broad base provides stability and strength, allowing the volcano to support the weight of a mountain with great height. Additionally, shield volcanoes are characterized by low viscosity lava, which flows easily and does not build up steep slopes. Therefore, they are capable of supporting a mountain with enormous height without collapsing.

After a violent eruption, a composite volcano stays relatively quiet for a long period of time. This is because the eruption releases a significant amount of built-up pressure and energy within the volcano. As a result, the volcano enters a dormant or inactive phase, where there is little to no volcanic activity. During this period, the volcano appears calm and quiet, with no signs of any imminent eruptions. This quiet phase can last for many years or even centuries before the volcano becomes active again.

Pyroclastic flows are high-speed mixtures of hot gas, ash, and volcanic fragments that can travel down the slopes of a volcano. They can reach speeds of up to several hundred kilometers per hour, making them extremely dangerous. The correct answer "Faster than 100 kilometers" implies that pyroclastic flows can travel at speeds exceeding 100 kilometers per hour, emphasizing their rapid and destructive nature.

A cinder cone is the simplest type of volcano because it is formed by a single eruption and consists mainly of loose volcanic fragments, such as cinders and ash. These fragments are ejected into the air and fall back onto the volcano's vent, building up a cone-shaped structure. Cinder cones are typically small in size and have steep slopes. They have a short lifespan and are often found alongside other types of volcanoes.

When two oceanic plates collide, they create a chain of volcanic islands. This is because when the plates collide, one plate is forced beneath the other in a process called subduction. As the subducting plate sinks into the mantle, it begins to melt due to the high temperatures and pressures. This molten rock, or magma, then rises to the surface and erupts, forming a volcanic island. Over time, as the plate continues to move and the volcano becomes inactive, a new volcano forms further along the plate boundary, creating a chain of volcanic islands.

A hotspot or hot spot is an area of volcanic activity that occurs when a plume of hot solid material rises from deep within Earth's crust. This plume of hot material creates a localized area of intense heat and volcanic activity, leading to the formation of volcanoes and other volcanic features. The terms "hotspot" and "hot spot" are used interchangeably to describe this geological phenomenon.

Shield volcanoes are characterized by the eruption of fluid basaltic lavas, which have low viscosity and flow easily. Due to their low silica content, these lavas do not trap gas bubbles, resulting in less explosive eruptions. Therefore, shield volcanoes are generally less explosive than other types of volcanoes, such as stratovolcanoes, which erupt more viscous lavas with higher silica content, leading to the buildup of gas pressure and more explosive eruptions.

A volcano with a broad base and gently sloping sides is known as a shield volcano. Shield volcanoes are formed by the accumulation of low-viscosity lava flows that spread out in thin layers, gradually building up the volcano's shape. This type of volcano has a characteristic shield-like appearance, with a wide base and gradual slopes. Shield volcanoes are typically not explosive and are associated with effusive eruptions, where lava flows steadily from the vent. They are commonly found in hotspots and are examples of basaltic volcanism.

Pahoehoe is solidified basaltic lava on land that has formed with smooth, rope-like surfaces. This type of lava flow is characterized by its low viscosity, which allows it to flow easily and form smooth, undulating surfaces as it cools and solidifies. The rope-like appearance is created by the movement of the still-molten interior of the flow, which causes the surface to fold and twist. Pahoehoe lava flows are commonly found in volcanic regions and are a result of the unique properties of basaltic lava.

Volcanoes are commonly found along mid-ocean ridges and subduction boundaries. Mid-ocean ridges are underwater mountain ranges where tectonic plates are moving apart, allowing magma to rise and form new crust. Subduction boundaries occur when one tectonic plate is forced beneath another, causing intense heat and pressure that leads to the formation of volcanoes. Therefore, the correct answer is Mid-Ocean Ridges and Subduction Boundaries.

Mount St. Helens exploded violently in 1980 after more than a century of being quiet. This means that the volcano had not erupted for more than 100 years before the 1980 eruption. The eruption was a result of built-up pressure and magma beneath the surface, which eventually led to a catastrophic explosion.

The correct answer is "Active" because active volcanoes are known to have calderas at their summits. Calderas are large volcanic craters that form when the magma chamber beneath a volcano collapses after an eruption. Active volcanoes are those that have erupted recently or are expected to erupt in the future, making them more likely to have calderas. Non-active and small volcanoes may not have the same level of volcanic activity or the necessary conditions for the formation of calderas. Similarly, while big volcanoes may have the potential for caldera formation, it is not a guarantee.

Early astronomers looking at the moon believed that the dark areas were seas. This was because these areas appeared smooth and dark, resembling bodies of water on Earth. They named these regions "seas" or "maria" in Latin, even though they were actually large plains of solidified lava. The term "seas" was used metaphorically to describe these areas, as early astronomers did not have the technology to accurately determine the moon's geological features.

The correct answer is "Solid" because the lithosphere, which is the rigid outer layer of the Earth, exerts pressure on the underlying asthenosphere. This pressure causes the asthenosphere to be in a solid state, despite the high temperatures present in this region.

Basaltic magma is characterized by its low silica content, typically ranging from 45% to 52%. Therefore, the correct answer is 50% as it falls within this range.

Magma is a molten mixture of rock, minerals, and gases that forms beneath the Earth's surface. When magma rises to the surface and cools, it solidifies into igneous rock. The gases trapped in magma are released during volcanic eruptions. The two main gases found in magma are water vapor and carbon dioxide. These gases are produced by the heating and melting of rocks, as well as the degassing of volatile elements and compounds within the Earth's mantle.

Cinder cone volcanoes tend to be smaller than other types of volcanoes because they are formed by explosive eruptions of gas-rich magma. These eruptions result in the ejection of pyroclastic material, such as ash and cinder, which accumulate around the vent and form a conical shape. Due to their explosive nature, cinder cone volcanoes do not typically reach the same size or height as other types of volcanoes, such as shield or composite volcanoes, which are formed by less explosive eruptions and have a more gradual slope.

The term volcano refers not only to a volcanic vent but also to the land form that develops as the materials from a volcanic eruption harden. This means that when a volcano erupts, the molten lava and other materials that are ejected from the vent cool and solidify, forming a new land form. Therefore, the correct answer is "Land form that develops as the materials from a volcanic eruption harden."

In the context of the question, "dark spots" are referred to as "Maria." Maria is the term used to describe the large, dark, flat areas on the Moon's surface, which were initially mistaken for bodies of water by early astronomers. The term "dark spots" is synonymous with Maria in the context of lunar geography.

Shield volcanoes are the most common type of volcanoes on Venus. These volcanoes are characterized by their broad, low-profile shape and are formed by the eruption of low-viscosity lava that spreads out in thin layers. They have gentle slopes and can cover large areas. This type of volcano is different from composite volcanoes, which are tall and steep, and cinder cone volcanoes, which are small and conical. Therefore, the correct answer is shield volcanoes.

The correct answer is 1720 Degrees Celsius. This is the highest temperature that may be reached at Pillan Patera.

Pyroclastic material is classified by its size. This classification is important as it helps scientists understand the characteristics and behavior of volcanic eruptions. The size of pyroclastic material can vary greatly, ranging from tiny ash particles to larger volcanic bombs. By studying the size distribution of pyroclastic material, scientists can determine the intensity of an eruption, the distance it can travel, and the potential hazards it may pose to surrounding areas. Therefore, size is a crucial factor in classifying pyroclastic material.

The correct answer is 15%. This means that only 15% of the moon's surface is covered by dark areas. The dark areas, also known as lunar maria, are large basaltic plains that were formed by ancient volcanic eruptions. The rest of the moon's surface is covered by bright, rugged highlands. The dark areas are more visible from Earth and give the moon its characteristic "man in the moon" appearance.

The appearance of hardened basaltic lava depends on the temperature and speed of the flow. The temperature determines the viscosity of the lava, with hotter temperatures resulting in more fluid lava flows. The speed of the flow also affects the texture and appearance, as faster flows tend to have smoother surfaces due to the rapid cooling and solidification of the lava. Therefore, the temperature and speed of the flow are key factors in determining the appearance of hardened basaltic lava.

A lava plateau is formed when basaltic lava flows out from a crack or fissure in the earth's surface and spreads over a large area, creating a flat or gently sloping landform. The lava cools and solidifies, forming layers of basalt rock that build up over time. This process can occur over millions of years, resulting in a vast expanse of basaltic rock that resembles a plateau. Lava plateaus are typically found in areas with volcanic activity and can cover extensive regions, showcasing the power and impact of volcanic eruptions.

Scientists estimate that hot spots are located between 670 kilometers to 2,900 kilometers beneath the surface. This range is based on geological studies and observations. Hot spots are areas of intense volcanic activity that occur due to a localized source of heat deep within the Earth's mantle. The estimated depth range suggests that these hot spots are located in the upper mantle or lower mantle.

The huge size of Olympus Mons, the largest volcano in the solar system, suggests that Mars does not have moving plates. On Earth, the movement of tectonic plates is responsible for the formation of mountains and volcanoes. However, Mars lacks the same type of tectonic activity, indicating that its volcanoes, including Olympus Mons, are not formed by plate movement. Therefore, the correct answer is moving plates.

One of the most volcanically active places in the solar system is IO, Jupiter's third largest moon. IO is known for its intense volcanic activity, with hundreds of active volcanoes erupting constantly. This is due to the tidal forces exerted by Jupiter and its other moons, causing immense heat and friction within IO's interior. The volcanic activity on IO is so intense that it has created a colorful and dynamic surface, making it a fascinating object of study for scientists.

At a subduction boundary, volcanoes always form on the overriding plate. This is because subduction occurs when one tectonic plate is forced beneath another, creating a convergent boundary. As the subducting plate sinks into the mantle, it generates intense heat and pressure, causing the mantle to melt. This molten rock, or magma, rises through the overriding plate, leading to the formation of volcanoes. These volcanoes are typically located parallel to the subduction zone and can create volcanic arcs, such as the Andes or the Cascades.

A composite volcano is formed by layers of hardened lava flows and pyroclastic materials. The term "composite" refers to the fact that these volcanoes are composed of multiple layers of different materials. The lava flows and pyroclastic materials build up over time, creating a steep-sided cone shape. These volcanoes are characterized by explosive eruptions due to the high viscosity of the lava, which causes gas build-up and pressure. Composite volcanoes are also known as stratovolcanoes and are typically found in subduction zones where one tectonic plate is forced beneath another.

A solidified basaltic lava flow on land that has formed with rough, jagged surfaces is called "Aa".