9: Volcanoes - Geosciences

9: Volcanoes - Geosciences

Learning Objectives

After completing this chapter, you should be able to:

  • Relate magma type with plate boundaries
  • Understand why most magma crystallizes underground
  • Associate volcano form with eruption type and magma type
  • Recognize the hazards associated with volcanoes
  • 9.1: Introduction
    How would you like to live on an active volcano? Surprisingly, a lot of people are living on or near active volcanoes, and many more live near volcanoes that are currently considered to be “dormant”. Are they crazy? Maybe some are, but not all volcanoes erupt explosively; for example, the type of volcano that forms the Hawaiian Islands is a type that erupts effusively, with lava running down the sides (flanks) of the volcano.
  • 9.2: Magma Generation
    In the previous chapter on igneous rocks, you learned about the concept of partial melting, and in the chapter on plate tectonics you learned about the conditions necessary for mantle rocks to melt; we will review these concepts in this section.
  • 9.3: Lab Exercise (Part A)
    Refer to Figure 9.4 to help answer the questions. The exercises that follow the use of Google Earth. For each question (or set of questions) paste the location that is given into the “Search” box. When finding your locations in Google Earth, be sure to zoom out to higher eye elevations in order to see all of the important features of each area.
  • 9.4: Magmatic Processes Occurring Within The Earth's Crust
    Once magma is generated by one of the mechanisms mentioned earlier (increased temperature, decreased pressure, or by adding water), the magma rises upward through the surrounding rock mainly through pre-existing fractures in the brittle lithosphere. A lot of magma stops rising upward through the continental crust because it has encountered an area in the crust that has the same density as the magma.
  • 9.5: Lab Exercise (Part B)
    The questions in this exercise demonstrate the control that tectonic setting has on the type of magma produced. For the Google Earth questions, copy and paste the latitude and longitude coordinates into the search bar (or just type them in).
  • 9.6: Magma Composition and Viscosity
    In the chapter on igneous rocks, you learned that the igneous rock classification is in part based on the mineral content of the rock. For example, ultramafic rocks are igneous rocks composed primarily of olivine and a lesser amount of calcium-rich plagioclase and pyroxene, whereas quartz, muscovite and potassium feldspar are the typical minerals found in felsic rocks.
  • 9.7: Lab Exercise (Part C)
    The following questions address what factors control how fast a magma or lava can flow. The resistance to flow (viscosity) depends primarily on the magma or lava composition but is also affected by temperature.
  • 9.8: Volcanic Landforms and Eruption Styles
    The size, shape, and eruptive style of any volcano ultimately depend on the magma composition. We will focus mainly on mafic and felsic magmas as intermediate magmas have properties that are intermediate between these two types, and ignore the ultramafic magma as this type no longer forms. As mentioned earlier, mafic magmas are lower in silica, causing low viscosity. As mafic magma erupts on to the surface through a central vent, the magma will spread out quite easily due to its low viscosity.
  • 9.9: Lab Exercise (Part D)
    The composition of magma or lava may also control what type of volcanic features or landforms are seen on the earth’s surface. In this exercise, you will use Google Earth to identify these landforms. Figures 9.9 through 9.11 may help you in this section. For the Google Earth questions, copy and paste the latitude and longitude coordinates into the search bar (or just type them in).
  • 9.10: Volcanic Hazards
    When comparing the two volcano types, shield and composite, it is obvious that although the shield volcanos are more massive, they are far less dangerous to the population than the smaller composite volcanoes. Shield volcanoes produce basaltic lavas that may fountain at the vent, due to gases, but end up flowing passively down the flanks of the volcano.
  • 9.11: Lab Exercise (Part E)
    Potential hazards associated with certain volcanic types can be identified using topographic maps or aerial photographs. In this exercise, we will use Google Earth.
  • 9.12: Student Responses
    The following is a summary of the questions in this lab for ease in submitting answers online.

Thumbnail: an aerial view of​ the​ Pu‘u ‘O‘o fountain during episode 23 of the Pu‘u ‘O‘o–Kupaianaha Eruption​ on July 28, 1984.​ Theodolite​ measurements of ​these ​high fountains, which played throughout the day, ranged from 150 to 305​ ​m​. (Public Domain; USGS via wikipedia).

Digging Deep into Geosciences with Minecraft

Building volcanoes, caves, and other features in an “open-world” computer game is an engaging way to teach the next generation about Earth.

Credit: Minecraft/Mojang, build by Mohi Kumar

By Laura Hobbs , Carly Stevens, and Jackie Hartley 29 October 2018

Imagine yourself in a world where everything is made up of cubes. Colorful blocks represent rocks, trees, water, and animals. An erupting volcano produces blocks of flowing lava. A cave contains cubes of iron and gold ore.

Sound familiar? This is the world of Minecraft, a hugely popular “open-world” construction-based video game in which players can move around freely and build virtual creations by “mining” and placing textured blocks with different properties. You can build elaborate cities and ships—even the Eiffel Tower or Tolkien’s Minas Morgul. You can also build a working computer that can perform calculations.

This is what we do at Science Hunters, an outreach program at Lancaster University in the United Kingdom. In the blocky world of Minecraft, we task players with building dinosaurs, rockets, volcanoes, caves, and even whole planets. From seeds to space, they can explore and relate the processes they interact with in the game to the real world around them.

In workshops run by Science Hunters, children use Minecraft to gain skills in creative thinking, problem solving, teamwork, and communication, all while exploring complex scientific concepts through experiences that are simply not possible in everyday life. How else can you play with molten lava?

Hot Cubes

Each Science Hunters workshop involves a theme, such as volcanoes or oceans. First, away from computers, we introduce the topic with hands-on demonstrations of real-world examples.

(top) In Minecraft’s creative mode, lava can be cast from a bucket onto the ground. (bottom) Pour a bucket of water in the vicinity of this lava, and the hottest parts will turn into obsidian, as seen here. Credit: Minecraft/Mojang, build by Mohi Kumar

For example, in the volcano theme, we show students real examples of obsidian, rhyolite, and pumice. We talk about their formation, along with hazards associated with them and how we might protect ourselves against these. Then we ask the students to enter the Minecraft world in creative mode and start building their own volcano.

Water, lava, and obsidian play a role in advancing objectives in Minecraft’s survival mode game play, so many students come to sessions with Minecraft-related knowledge of these block types. For example, water and lava blocks in Minecraft flow downward and spread out—just like they would under Earth’s gravity—and vegetation may be set alight by lava. We take that baseline knowledge and help the student go steps farther.

In real life, obsidian—volcanic glass—can form when lava comes in contact with water and cools instantly, so that crystals do not have time to develop. In Minecraft’s creative mode, obsidian can form when you take a bucket of lava from your inventory and cast it over the ground. The lava mounds into a tiny hill the “source” and hottest part of the lava flow, from which the mound is “erupting,” is the very first lava block you placed down from your lava bucket. Cast a bucket of water—also found in your inventory—near that source of lava, and if the water hits it, that source block will turn into obsidian. Other blocks in the lava flow, moving outward from this source block, are coded to be not as hot these blocks will solidify as the water runs over them, but they do not create obsidian. Instead, they turn into blocks that represent crystalline lava rocks.

We encourage students to create volcanoes complete with plumbing, eruptions, lava-water interactions, and external structures that need protecting from hazards when they erupt. These behaviors reflect real-world geologic processes, which gives us an opportunity to talk with the children about the differences between crystalline rocks and volcanic glass, crystal sizes and growth rates, subaerial and subaqueous cooling, and properties of dynamic flows and solid rocks. We also talk about the impact of the volcano they build on the ecosystem surrounding it and villages nearby.

We discuss all these things while the students dig, build, and play. Each session revolves around a Minecraft challenge. In the volcano theme, we encourage students to create volcanoes complete with plumbing, eruptions, lava-water interactions, and external structures that need protecting from hazards when they erupt.

The World in Blocks

We use a version of Minecraft specifically designed for educational use, which means that we can ensure that game play functionality is appropriate for the classroom. Operating the game in its creative mode is key: This mode gives players an unlimited number and very wide range of blocks to build with. It also means that players don’t have to keep themselves alive in the game, as they would in its survival mode. Another perk is that players can fly around in their virtual world.

Through Science Hunters, we invite students to imagine with us. In addition to the class on volcanoes, we run a variety of other sessions, each focused on a different theme: dinosaurs, caves and minerals, rockets, planets, mining, ice and snow, and oceans, to name a few.

For example, we guide children through dinosaur and pterosaur classifications and use scientifically accurate toys as well as templates of real dinosaur footprints to show sizes and scales of dinosaur features. The students then use this information to build a model of a Mesozoic creature, either reconstructing a known example or designing their own.

A student-designed model of a pterosaur, created in a Science Hunters workshop. Credit: Minecraft/Mojang, build by Science Hunters

In a different session, we show children a variety of mineral samples, discuss the differences between stalagmites and stalactites, and then set them to work to dig down and construct their own caves. Going extraterrestrial, we show students models of the structure of the solar system and of individual planets. Then, using a planet-themed Minecraft world and a resource pack that enable a virtual space environment, students can build their own planets from core to crust.


Minecraft can be used as a teaching tool to construct more than just natural features. It can help teach students how the built environment—buildings, agriculture, transportation routes—influences nature.

For example, how are we going to produce enough healthful food in the future, as our population expands and builds on the very farmland we need to produce that extra food? Through one of our classes, children inspect raw, unprocessed real-world samples of foodstuffs represented in Minecraft. Then they design and build their space-saving solutions to this dilemma in the game, making use of the game’s crops, which respond to sources of light, water, and fertilizer as they grow.

In other sessions, we give students a tour of Lancaster University’s own wind turbine. We examine its energy production through statistics and the turbine’s online live data feed to demonstrate generation and use of renewable energy. Then we ask the children to design and build renewable energy production mechanisms. This can be a stand-alone task or an expansion of our exploration of town planning, in which children build their own cities, including power networks, onto grid systems.

A Minecraft wind turbine, modeled after a real instrument at Lancaster University. This virtual turbine was built at the Science Hunters’ regular Minecraft Club, aligned with the current wind direction at the time based on live data from the university’s turbine. The real turbine can be seen by all attendees as they travel to and from club sessions. Credit: Minecraft/Mojang, build by Science Hunters

Built environment lessons can also envision scenarios off our world. After leading students through a discussion on what they’d need if they were to live on another planet, we turn students loose in a premade barren Minecraft landscape, reminiscent of Mars or the Moon, to design their own space station.

Virtual Ecology

Minecraft contains a range of representative ecological biomes, so we created instructional packets containing booklets, posters, and stickers that we sent out across the United Kingdom (with the support of the British Ecological Society) to guide families through ecological explorations on their own time at home. We supply an introduction to biomes and their associated animals, plants, habitats, and foods, all clearly linked to the equivalent features in Minecraft, with building challenges to complete in Minecraft along the way.

We also provide a series of experiments and identification activities. For example, we give families seeds to grow cacti and food crops found in Minecraft, along with fertilizer to demonstrate how, just like in the game world, real plants can get a growth boost when fertilizer is added. We also provide some wood samples of tree species present in the game, linked to information about the biomes in which those trees are found.

Students can roam around snowy Minecraft plains, designing their own intricate models of radially symmetric snowflakes. Our workshops also investigate flora and fauna through Minecraft, delving into how organisms adapt to their environments. We first experiment, outside of the game, with analogies such as insulated versus noninsulated beakers of water to explore heat retention and loss, to which animals adapt through features such as fur coats and large ears. Then we ask students to use these concepts to build an animal that would flourish in the Minecraft biome they are playing in.

Cold biomes are particularly useful as a basis for discussing how snow and ice form, why igloos are not cold inside, and why every snowflake is unique. In our sessions, students can roam around snowy Minecraft plains building igloos and designing their own intricate models of radially symmetric snowflakes.

A student-designed snowflake model, built in Minecraft using virtual blocks of snow. Credit: Minecraft/Mojang, build by Science Hunters

At other times, we dive into ocean environments, exploring the undersea world and learning about its inhabitants in our own seas before students build their own seascapes. This topic also offers a great opportunity to talk about pollution, plastics, and microplastics in the oceans, and from there students often turn to considering their own environmental impacts.

Geosciences Through Gaming

Science Hunters activities take place in schools, at public events such as community festivals, and at a regular on-campus club offered to local children with autism. We work with children of all ages, with a core audience of around 7–11 years, in several different areas of the United Kingdom. Our team encourages children to play in pairs to support their development of social communication and teamwork skills.

We aim to embed the idea that science learning can be fun, engaging, and open to anyone. We also hope to inspire an interest in science beyond the confines of the classroom.

Minecraft is an ideal medium for science outreach and engagement, as it is generally very popular with children. Lane and Yi [2017] described it as one of the most widely used and important games of the current generation. Just a mention of the game draws children’s attention and interest.

Learning by Playing

Science Hunters aims to make science learning fun and accessible to everyone. Here a 7-year-old girl examines a slide using a research microscope at a Science Hunters public event. Credit: Steve Pendrill

Since the program’s inception in 2014, feedback collected from all areas of the project has been overwhelmingly positive. Children appreciate the opportunity to explore new topics, participate in hands-on demonstrations, and ask in-depth scientific questions to people with relevant scientific knowledge and expertise. They tell us that using Minecraft makes the session fun and different from their usual lessons and helps them to understand the topics. And when we ask them to tell us something that they’ve learned, every one of them can do it. We’ve even heard “This is the best day of my life!”

Parents and teachers often tell us that during Science Hunters sessions, children who often find it difficult to participate in standard lessons are engaged and absorbed in the session. We’ve seen enthusiastic teamwork from children whom we’ve been told have a history of interacting poorly with others. Some of these students even high-five their partners at the end of the lesson. In addition, we’ve found that through using Minecraft, children can both demonstrate what they’ve learned within the session and, by consolidating their learning through the game, remember it later.

Inspiring the Next Generation

For more information, access to our program, and ideas about how to structure Minecraft-based geoscience learning for your students, your children, or yourself, visit our website or contact us directly.

9: Volcanoes - Geosciences

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In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet. This means that the sill does not cut across preexisting rocks, in contrast to dikes, discordant intrusive sheets which do cut across older rocks. Sills are fed by dikes, except in unusual locations where they form in nearly vertical beds attached directly to a magma source. The rocks must be brittle and fracture to create the planes along which the magma intrudes the parent rock bodies, whether this occurs along preexisting planes between sedimentary or volcanic beds or weakened planes related to foliation in metamorphic rock. These planes or weakened areas allow the intrusion of a thin sheet-like body of magma paralleling the existing bedding planes, concordant fracture zone, or foliations.

Figure 6. Illustration showing the difference between a dike and a sill.

Sills parallel beds (layers) and foliations in the surrounding country rock. They can be originally emplaced in a horizontal orientation, although tectonic processes may cause subsequent rotation of horizontal sills into near vertical orientations. Sills can be confused with solidified lava flows however, there are several differences between them. Intruded sills will show partial melting and incorporation of the surrounding country rock. On both contact surfaces of the country rock into which the sill has intruded, evidence of heating will be observed (contact metamorphism). Lava flows will show this evidence only on the lower side of the flow. In addition, lava flows will typically show evidence of vesicles (bubbles) where gases escaped into the atmosphere. Because sills generally form at shallow depths (up to many kilometers) below the surface, the pressure of overlying rock prevents this from happening much, if at all. Lava flows will also typically show evidence of weathering on their upper surface, whereas sills, if still covered by country rock, typically do not.

Associated Ore Deposits

Figure 7. Mid-Carboniferous dolerite sill cutting Lower Carboniferous shales and sandstones, Horton Bluff, Minas Basin South Shore, Nova Scotia

Certain layered intrusions are a variety of sill that often contain important ore deposits. Precambrian examples include the Bushveld, Insizwa and the Great Dyke complexes of southern Africa, the Duluth intrusive complex of the Superior District, and the Stillwater igneous complex of the United States. Phanerozoic examples are usually smaller and include the Rùm peridotite complex of Scotland and the Skaergaard igneous complex of east Greenland. These intrusions often contain concentrations of gold, platinum, chromium and other rare elements.

Transgressive Sills

Despite their concordant nature, many large sills change stratigraphic level within the intruded sequence, with each concordant part of the intrusion linked by relatively short dike-like segments. Such sills are known as transgressive, examples include the Whin Sill and sills within the Karoo basin. [4] The geometry of large sill complexes in sedimentary basins has become clearer with the availability of 3D seismic reflection data. [5] Such data has shown that many sills have an overall saucer shape and that many others are at least in part transgressive. [6]

Other Meanings

“Sill” may also refer to the rise in depth near the mouth of a fjord caused by the terminal moraine of the previous glacier.

Geology 9

Guatemala City - Guatemalan authorities issued a danger warning on Wednesday in response to intensifying activity in the country's Fuego Volcano. The danger warning issued by the government was one step short of a declaration of emergency requiring evacuation of the communities around the volcano.

Volcano de Pacaya-Guatemala

Pacaya, which in recent years has consistently erupted olivine-bearing high alumina basaltic lavas, erupted with remarkable violence on both 27 and 28 May 2010 with an explosion on the 27th lasting

45 minutes. This was followed by a smaller explosion the next day that generated a plume assessed from satellite and meteorological data as reaching 13 km altitude. In this report we describe those events as explosions in order to distinguish them from the ongoing, decades-long, and often effusive eruption generally seen at Pacaya. The terms ‘explosion’ and ‘explosive’ appear warranted given such factors as the suddenness of escalation, the

10 km over the summit when measured during the weaker explosion on the 28th, the density of projectiles, and the scale of the tephra fall. The term explosion seems consistent with common practice (Sparks, 1986 Fiske and others, 2009).
Pacaya , which has a record of eruptions dating back over 1,600 years, has been erupting the majority of the time since 1961, often emitting rough-surfaced lavas but also occasionally discharging explosions. The centerpiece of the National Park of the same name, it is the most often climbed volcano in Guatemala. There have been 69 prior Smithsonian-published reports describing behavior from 1969 to early January 2010 (CSLP 03-70 to BGVN 34:12). REW (2013) ranked the 27 May explosions as sub-plinean and the associated lava emissions as the largest since similar events in 1961.

2,000 residents to evacuate and injuring 59 people. A high density of ballistics fell on nearby hamlets and villages, particularly those 2.5-3.5 km N of the MacKenny cone (El Cedro, San Francisco de Sales, and Calderas). The ballistics had sufficient mass and velocity to puncture roofs with a density on the order of one puncture per square meter in some places. Many more smaller ballistics bent but did not penetrate the corrugated sheet metal roofs common in many of the region's dwellings. Some of the ballistics were sufficiently hot to start fires. A sh caused widespread damage locally, and up to

8 cm of ash fell on parts of metropolitan Guatemala City, the nation’s capital, centered

35 km NNW of Pacaya. Up to 20 cm of tephra accumulated at and near Pacaya. According to available census data, the population within 10 km of Pacaya was 57,000 (John Ewert, USGS-CVO, personal communication).


The papier-mâché volcano is a real classic, but there are many other ways to make an even more exciting and interesting science project focused on volcanoes!

To get started on your own volcano-based science project, you will want to first have an understanding of how volcanoes form. This is related to tectonic plates. The entire outer shell of the Earth, known as the lithosphere, is made up of tectonic plates that are constantly moving. There are seven or eight large tectonic plates and many more minor ones. The low parts of the plates are beneath the world's oceans, and the high parts of the plates are landmasses. New plate material is generated at deep sea ocean ridges in a process called sea-floor spreading. Material from plates is also recycled at trenches, where dense, oceanic crust dives back underneath an adjacent plate towards the upper mantle. This subduction of one plate beneath another can provide the massive force to produce uplift of mountain ranges. Overall, where tectonic plates meet and bump together, it is common to find mountains, mid-ocean ridges, earthquakes, and volcanic activity. (What forms depends on how exactly the tectonic plates are moving against each other at the plate boundary.)

The theory of plate tectonics was actually long debated, and detailed mapping studies of cooled molten rocks helped clinch the case. Rocks containing magnetic material reveal the history of when and where they formed. As the molten rocks cooled, the magnetic particles aligned themselves with the Earth's magnetic field at that time. Armed with that information, geologists have been able to map the dates of origin of the oceanic crust, and to confirm that sea-floor spreading at suboceanic ridges and subduction at trenches is a constant process. Although the mechanism for the motion of the tectonic plates is still not well understood, it is thought that convection of heat from the Earth's core is somehow involved.

In this geology science project, you will investigate an aspect of volcanoes, such as by mapping volcanic activity, predicting volcanic eruptions, or developing a realistic volcano model. Which volcanoes are active volcanoes, and just how active are they? Where are the most dangerous volcanoes located? Does volcanic activity follow a certain pattern, such as based on time or location? Does this correlate with the presence of tectonic plates? Can you develop a more dynamic and accurate volcano model based on your understanding of how volcanoes function? You could do your science project on other parts of volcano-based science, such as eruption warning systems, volcanic minerals, and volcanic gases. What are the best monitoring strategies for predicting volcanic activity and developing a useful warning system? Which types of gases come out of a volcano? To find out more about volcanic activity, how to predict volcanic eruptions, and to view data about current and historical volcanic activity, you can visit the United States Geological Survey (USGS) website listed in the Bibliography in the Background tab.

Composite Volcanoes

Composite volcanoes are made of felsic to intermediate rock. The viscosity of the lava means that eruptions at these volcanoes are often explosive (figure 2).

Figure 2. Mt. Fuji, the highest mountain in Japan, is a dormant composite volcano.

The viscous lava cannot travel far down the sides of the volcano before it solidifies, which creates the steep slopes of a composite volcano. Viscosity also causes some eruptions to explode as ash and small rocks. The volcano is constructed layer by layer, as ash and lava solidify, one upon the other (figure 3). The result is the classic cone shape of composite volcanoes.

Figure 3. A cross section of a composite volcano reveals alternating layers of rock and ash: (1) magma chamber, (2) bedrock, (3) pipe, (4) ash layers, (5) lava layers, (6) lava flow, (7) vent, (8) lava, (9) ash cloud. Frequently there is a large crater at the top from the last eruption.

Recent Eruption

Kīlauea Volcano began erupting on December 20, 2020, at about 9:30 p.m. HST in Halema‘uma‘u crater. The last activity on the lava lake surface was observed on May 23 and on May 26, 2021, the USGS Hawaiian Volcano Observatory lowered the Volcano Alert Level for ground-based hazards from WATCH to ADVISORY and the Aviation Color Code from ORANGE to YELLOW.

Current Kīlauea Updates

See the most recent volcano update for Kīlauea.

Photo & Video Chronology

A series of posts showing photos and videos from Kīlauea.


Webcams show current conditions on Kīlauea.

Graph showing the depth of the Halema‘uma‘u crater lava lake at Kīlauea Volcano's summit. Measurements began one day after the start of the eruption on December 20, 2020 and are updated by geologists making observations from the field. HVO field crews use a portable laser range finder to measure the vertical distance between points of known elevation and the lava lake surface. Frequent sets of repeat manual measurements were averaged and plotted to derive the lava lake depth.

On January 8, 2021, a novel laser rangefinder was stationed at Kīlauea Volcano's summit. The fixed instrument continuously measures the distance to the lava lake surface, and telemeters data to HVO in real time. The raw data has been edited for this graph, with a running mean average filter of 3600 seconds.

Variations in plotted depth can occur due to alternating field crews, the uneven surface of the lava lake, or laser rangefinder returns on gas rather than the lake surface.

Sulfur dioxide (SO2) emission rates measured using an upward-looking ultraviolet spectrometer. These data are collected by traversing the gas plume in a vehicle or helicopter, downwind of Halema‘uma‘u, generally within and/or southwest of Kīlauea caldera. Results from multiple traverses during a day are averaged to yield the emission rates shown here. Successful measurements depend on wind, weather, and staff availability. Values are preliminary and are subject to revision.

Lastest eruption map

See additional maps on the Kīlauea Maps Page

This map of Halema‘uma‘u at the summit of Kīlauea shows 20 m (66 ft) contour lines (dark gray) that mark locations of equal elevation above sea level (asl). The map shows that the lava lake filled 229 m (752 ft) of the crater, to an elevation of 747 m (2450 ft) asl, from the beginning of the eruption on December 20, 2020, through May 13, 2021. Over this period, a total of 41 million cubic meters (11 billion gallons) of lava was erupted into the crater, filling approximately 5 percent of the volume that collapsed within the caldera during the 2018 eruption. The graphic at the bottom shows topographic profiles from west to east across the caldera before 2018, shortly after 2018, and as of May 13, 2021, along with the 2019-2020 Halema‘uma‘u water lake. The last activity on the lava lake surface was observed on May 23 and on May 26, 2021, the USGS Hawaiian Volcano Observatory lowered the Volcano Alert Level for ground-based hazards from WATCH to ADVISORY and the Aviation Color Code from ORANGE to YELLOW. USGS map.

NPS Landscapes Developed at Hotspots

Two prominent hotspot tracks appear on a map of the 50 United States, one involving a plate with thin oceanic crust (Hawaii), and one with thicker continental crust (Yellowstone).

Shaded relief map of United States, highlighting National Park Service sites at Hotspots. Letter codes are abreviations for park names listed in tectonic settings pages linked below. Sites in Hawaii and American Samoa lie on thin oceanic crust, whereas thicker continental crust is associated with the hotspot track in the Columbia Plateau of Oregon and Washington, the Snake River Plain of Idaho, and the current position of the Yellowstone Hotspot beneath Yellowstone National Park.

Modified from “Parks and Plates: The Geology of our National Parks, Monuments and Seashores,” by Robert J. Lillie, New York, W. W. Norton and Company, 298 pp., 2005,

Hawaii Volcanoes National Park, Hawaii. Fluid basalt lava erupts where the Pacific Plate, capped by thin oceanic crust, rides over the Hawaiian Hotspot.

The Hawaiian Islands are broad and high at the southeast, becoming smaller and lower to the northwest. Two national parks, Haleakala on Maui and Hawaii Volcanoes on the Big Island called Hawaii, represent different stages of passage of the Pacific Plate over the Hawaiian Hotspot. National Park of American Samoa reveals another volcanic island chain formed as the Pacific Plate moves over a different hotspot.

Yellowstone National Park, Wyoming/Montana/Idaho. The Grand Canyon of the Yellowstone River is carved through rhyolite lava flows from the explosive Yellowstone Supervolcano, forming as the North American Plate, capped by thick continental crust, rides over the Yellowstone Hotspot.

Photo courtesy of Robert J. Lillie.

On the North American continent the Snake River Plain of southern Idaho connects the Columbia Plateau region of southeastern Washington and northeastern Oregon with Yellowstone National Park in the northwest corner of Wyoming. Extensive basalt lava flows at John Day Fossil Beds National Monument in Oregon represent the initial surfacing of the Yellowstone Hotspot. Progressively younger volcanic rocks across southern Idaho record the west-southwest movement of the North American continent across the hotspot. The spectacular geysers, hot springs and other hydrothermal features in Yellowstone National Park illustrate that the hotspot is still alive and well.

Earth's Dynamic Geosphere: Volcanoes Activity 1- Where are the Volcanoes

Think about how you can help the audience understand why you chose the probable location of the volcanic eruption for your story. Use the following resources to find the volcanic eruptions in California.

    Reviews the basics of platetectonics and examines closely submarine volcanoes at divergent and convergent boundaries and hot spots. The site has good images of underwater lava flows as well as images of the organisms that live near these submarine volcanoes.
    Site includes a general overview of submarine volcanic eruptions as well as information about specific underwater volcanoes including the volcanoes of the Juan de Fuca ridge in the Pacific, Kavachi of the Solomon Islands, Kick 'Em Jenny of the West Indies, the Loihi Seamount of Hawaii, and Surtsey and the Vestmannmaeyjar volcanics of Iceland.

    Review the major types of volcanoes, including calderas, cinder cones, composite volcanoes, statrovolcanoes, and shield volcanoes. Provides links for further details and information about specific eruptions.

USGS Volcano Hazards Program, Read about volcanism in the following US states:

Watch the video: Physical Geology- Volcanoes vol. 1