What is a Volcano?
A volcano is a landform (usually a mountain) where molten rock erupts through the surface of the planet.
In simple terms a volcano is a mountain that opens downward to a pool of molten rock (magma) below the surface of the earth. It is a hole in the Earth from which molten rock and gas erupt.
What is the difference between lava and Magma?
Magma is liquid rock inside a volcano.
Lava is liquid rock (magma) that flows out of a volcano. Fresh lava ranges from 1,300° to 2,200° F (700° to 1,200° C) in temperature and glows red hot to white hot as it flows.
What are the three layers the Earth is made of?
The crust is the outer layer of Earth. It is about 18 miles thick. It is the part we live on.
The second layer is called the mantle. It is about 1,800 miles thick.
The inner layer is called the core.
What causes volcanoes to erupt?
1. The Earth’s crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move.
2. Between the Earth’s crust and the mantle is a substance called magma which is made of rock and gases.
3. When two plates collide, one section slides on top of the other, the one beneath is pushed down. Magma is squeezed up between two plates.
4. In many locations the hot molten magma from deep within the Earth rises up through the crust to reach the surface. This sometimes happens in the middle of plates. When a hot spot forms in the middle of a plate, it remains constant, as the plate continues to move over it. The result is that a trail of volcanoes is left behind, with older volcanoes moving away from the hot spot, and newer ones forming over top of the hot spot. Like in Canary Islands.
5. Not all volcanic activity takes place in volcanoes. In fact, more lava has reached the surface of the Earth through fissures in the Earth’s crust, than through volcanoes.
Explosive and Effusive Eruptions
When volcanic activity takes place above ground, so that hot molten magma is released onto the landscape, we say that the volcanic activity is extrusive, meaning it is on the exterior, or outside of the Earth. Magma that reaches the service is known as lava.
Lava flows are extraordinarily hot, and destructive. In many cases, these lava flows are slow and continuous, as is the case with the volcano on the Hawaiian Island. Hot lava flows year after year down the volcano, creating new terrain, rarely exploding (Effusive Eruption). In other cases, volcanoes can erupt with unbelievable force and power. These types of eruptions can send lava, rock, and hot ash, known as pyroclastic material shooting outward for hundreds of square miles, in some cases, even sending up a worldwide cloud of dust and ash. (Explosive Eruption)
One example of such an eruption is the island of Krakatua. In 1883 this island volcano exploded in a colossal event that completely destroyed the island, leaving nothing but ocean behind. The noise from the explosion washeard as far as 1,500 miles away, and dust filled the sky worldwide, creating beautiful sunsets for months.
ART & SCIENCE
1- Can you identify the artists of these paintings?
2- Is there any connection between our geology chapter and the following paintings ?
What causes some volcanoes to explode in devastating and deadly eruptions, while other volcanoes calmly pour their lava across the landscape with virtually no explosions what-so-ever?
The most important factor that determines what type of eruptions that a volcano will experience is chemistry. In other words, the substances found in the magma determine how it will erupt. A volcano whose molten magma contains large amounts of a substance called silica tend to explode with great energy. Volcanoes that contain little or no silica usually do not explode, but instead calmly release rivers of lava across the landscape. Volcanoes do not typically change their eruption type. Volcanoes that explode, will always explode, while those that release their lava in calm flows, will always do so. Be careful! Even when magma is very acid (large amounts of silica ) if it comes degassed won’t produce explosive eruptions. Example: Black lava of Teide.
Volcanoes and Land Formation
Volcanoes create an almost infinite variety of landforms and terrain. However, geologists have noticed patterns when studying these different terrains, that allow them to group them into categories, based on how they are the same, and how they are different. These four landform types are called lava flows, volcanic peaks, calderas, and volcanic necks.
Lava flows get their name from the manner in which the hot molten lava flows outward parallel to the surface of the Earth. The result is a large flat lava covered plain.
A volcanic peak is what we tend to think of when we talk about volcanoes. It is a volcano that has formed a large cone shaped hill, or mountain. These cones typically have a large bowl shaped crater in the top center.
Calderas are massive crater-like depressions that can cover many tens of square miles. These calderas form when volcanoes explode with terrible destruction, completely obliterating the original volcano, and surrounding area.
One famous example of a caldera is caldera de Bandama in Gran Canaria.
A volcanic neck is the remnant of an old volcano. As the volcano died, the last bit of lava inside of the volcanoes opening, or neck, cooled and hardened. Over many hundreds of thousands of years the material around the neck is removed by erosion, leaving only the harder neck behind.
Effect of Volcanoes on people and the environment
Volcanoes can have a very serious effect on the lands and people around them when they erupt.
- Buildings are destroyed and people are made homeless.
- People are killed.
- Clouds of ash cover plants making them inedible.
- Poisonous gases kill people and animals.
- Dust causes pneumonia and illnesses to the survivors.
- Dark skies, severe winds and heavy rains may follow an eruption for months afterwards.
- People set up homes on the slopes of volcanoes because of the rich, fertile soil produced.
Types of Volcanoes
There are 3 different types of volcanoes:
1. Active – eruptions can be anytime and often.
2. Dormant – has been a while since it has erupted, but could at anytime.
3. Extinct, meaning it hasn’t erupted in a very long, long time so it probably won’t ever again.
The different parts of a Volcano
The images below shows the different parts of a volcano.
Be careful!: when the image show layer of ash it really means pyroclastic material.
What is Pyroclastic Material?
There are many types of pyroclastic material ejected during a volcanic eruption:
Ash is the most common pyroclastic rock material ejected during an eruption. Volcanic ash is so fine (< 2 mm) that it can be blown into the atmosphere and picked up by the jet stream where it can circle the Earth for several years.
Lapilli are pea-size to walnut-sized pieces of volcanic rock. (64mm – 2 mm)
Lava bombs are volcanic rocks larger than 64 mm in size.
Lava blocks are the largest pieces of pyroclastic material ejected during a violent eruption.
Pumice is igneous rock blown into the air in a semi-liquid state. The rock cools so fast it does not have time to crystallize. Gas bubbles inside the molten lava expands producing a rock that resembles a sponge.
What is the Ring of Fire?
Over half of the world’s volcanoes arise in a belt around the Pacific Ocean called the Ring of Fire.
History of science
This vocabulary word list will help you to study the most common and frequently tested words
Interactive whiteboard exercises (also .pdf)
VOLCANOES EXERCISE 1.ESB
VOLCANOES EXERCISE 1 (pdf)
VOLCANOES EXERCISE 2 ESB
VOLCANOES EXERCISE 2 (pdf)
VOLCANOES EXERCISE 3.ESB
VOLCANOES EXERCISE 3 (pdf)
Here you have some student’s videos to summarize Lanzarote trip. Enjoy it!
Un article de Romane C. et Elisa M., élèves de 2de.
Cette année sportive a tremblé sous l’onde de choc Armstrong : le cycliste américain convaincu de dopage a vu disparaître ses sept titres de champion du Tour de France, remettant sur le devant les enjeux du dopage. Son nom vient ainsi s’ajouter à une longue liste de grands sportifs qui se sont dopés. Et les sportives ? Ce thème est très peu abordé alors qu’elles sont aussi importantes que les hommes dans le monde du sport !
Nous n’avons pas d’énorme cas comme celui d’Armstrong, mais évidemment, des femmes sportives se sont faites contrôler positives, même si on en parle peu et peu souvent. Il y a des noms qui ont marqué l’histoire du dopage féminin, comme Marion Jones, Katerina Thanou ou encore Rebecca Gusmao et la chinoise Ye Shiwen qui est soupçonnée d’avoir pris de la drogue avant un 400 mètres.
Marion Jones a fait une grande carrière dans le sprint, remportant de nombreuses victoires lors, avant d’être reconnue coupable de dopage.
Katerina Thanou, quand à elle, malgré des blessures à répétition, elle remporte une médaille d’argent derrière Marion Jones. Mais comme Marion à confirmé son dopage le CIO proposa a Thanou de récupérer la médaille d’or, mais en 2004 elle avoua elle aussi son dopage.
Rebecca Gusmao, la nageuse a été contrôlé positive à la testostérone suite à des contrôles antidopage. La nageuse s’est vu retirer ses quatre médailles.
Ce ne sont que quelques exemples mais il y en eu d’autre. On compte seulement 1% de femmes dopées de moins que d’hommes. Donc même si le milieu sportif est très clairement « macho » du moment qu’ils rentrent dans le milieu de la compétition leur seul but est de gagner, et hommes comme femmes sont prêts à tout pour.