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Divergent plate boundaries exist where tectonic plates move away from each other. Divergence occurs between only oceanic or only continental plates, not one of each. The vast majority of divergent boundaries are found in the ocean.

In divergent zones, the plates are pulled, and not pushed, apart. The main force driving this plate motion is the "slab pull" that arises when plates sink into the mantle under their own weight at subduction zones . This pulling motion uncovers the hot deep mantle rock of the asthenosphere.

As the pressure eases on the deep rocks, they respond by melting, even though their temperature may not change. This process is called adiabatic melting. The melted portion expands and rises, having nowhere else it can go. This magma then freezes onto the trailing edges of the diverging plates, forming new Earth.

Example : Southern boundaries of the Australian plate and the southern and eastern boundaries of the Pacific plate

Divergent plate boundaries can be found at oceanic-oceanic plate boundaries (DPB I) and continential-contnential plate boundaries (DPB II)

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(DPB I) Oceanic-oceanic plate divergence

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(DPB I) Oceanic-oceanic plate divergence

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At the diverging plate boundaries of oceanic-oceanic plates, fractures are formed at the plate boundary and magma rises from the mantle to form new sea floor between the plates as they move apart. This process known as sea-floor spreading, occurs when magma flows out onto the sea-floor at the zone of divergence and cools after solidifying.

This forms a mid-oceanic ridge, a central ridge structure that divides the ocean basin in half. The new rocks are closer to the mid-oceanic ridge and are thus younger than those further away.
Example : The Mid-Atlantic Ridge in the middle of the Atlantic ocean that was formed when the North American Plate and Eurasian Plate moved away from each other https://www.youtube.com/watch?v=sgDM6m0lUGY

At various points along the mid-oceanic ridge, magma builds up and solidifies to form undersea volcanoes. Over time these volcanoes grown above sea level and become volcanic islands
Example : The Azores in the North Atlantic Ocean that is situated 850 miles off the shores of Portugal and that is made up of 9 volcanic islands https://www.youtube.com/watch?v=1fKiLr4m07k

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Diverging plates can cause landmasses to break up as plates diverge, they stretch and this causes fractures to form on the continental crust. As the continental crust is pulled apart further, the land between the two continental plates sinks and a linear depression known as a rift valley is formed.

Example :  The East African Rift Valley System (East African Rift System). Formed when the Nubian Boundary of the African plate diverged from the Somalian Boundary of the African plate. This system consists of a number of rift valleys each about 30 to 60 kilometres and a number of active volcanoes and earthquake fractures can also be found here.

This video shows how the formation of these rifts have affected the lives of those living in Kenya : https://www.youtube.com/watch?v=X13ntFfwXqY

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Scientists detect deep carbon emissions associated with continental rifting

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Convergent plate boundaries exist where two tectonic plates move towards each other and become faulted, folded and sometimes subducted (Where one plate slides beneath the other) and this collision of tectonic plates causes the formation of volcanoes.

Example : Along the north of the Pacific plate and North American plate. Between the Philippine plate and Eurasian plate

Convergent plate boundaries can be found at oceanic-oceanic plate boundaries (CPB I), continental-continental plate boundaries (CPB II) and oceanic-continental plate boundaries (CPB III).

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(CPB I) Oceanic-oceanic plate divergence

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(CPB I) Oceanic-oceanic plate divergence

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When two oceanic plates converge and collide, the denser plate subducts under the less dense plate. The location that this occurs is known as the subduction zone and at this subduction zone a depression in the ocean floor also known as a deep oceanic trench is formed.

The denser subducting plate causes the mantle material above it to melt and form magma. Magma then rises through the crust and forms volcanoes. Eventually, a chain or arc of islands will be formed. Earthquakes may also occur at the boundary between the two plates due to friction between the moving rock masses when a plate subducts under another.

Example : Where the Pacific plate converges with and subducts under the slower moving Philippine plate, forming the Mariana Trench and the Mariana Islands

This video gives us a brief overview of how the Mariana Trench was formed, the attempts made to venture deep into the Mariana Trech in the name of exploration as well as the unique sealife that resides deep in the Mariana Trench : https://www.youtube.com/watch?v=VoEVezcE0k0 (Time 1:18 to 2:40 explains how the Mariana Trench was formed)

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Two continental plates may collide and push against each other, resisting subduction due to the thickness and buoyancy of both plates making subduction impossible. This causes the plates the break and fracture in the crust. Layers of rock on the upper part of the crust are compressed tis causes massive folding where layers of rock fold upwards or sideways creating fold mountains.

Example : Between the Indian and Eurasian plates, causing the formation of the Himalayas. This video shows an time-lapse animation of how the Himalayas were formed over 70 Million years : https://www.youtube.com/watch?v=HuSHOQ6gv5Y

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(CPB III) Oceanic-continental plate convergence

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(CPB III) Oceanic-continental plate convergence

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When an Oceanic plate converges with a Continetal plate, the denser Oceanic plate subducts under the less dense Continental plate. An Oceanic Trench is then formed at the subduction zone while fold mountains are formed on the continental plate.

Active volcanoes are formed on the continental plate when magma below the crust rises to the surface, thus giving rise to the formation of volcanoes and the occurance of volcanic eruptions.

Example : Near Sumatra where the Australian plate subducts under a section of the Eurasian plate, causing the formation of the Sunda Trench.

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A volcano is an opening or rupture in the earth’s surface that allows magma (hot liquid and semi-liquid rock), volcanic ash and gases to escape. They are generally found where tectonic plates come together or separate but they can also occur in the middle of plates due to volcanic hotspots and can occur on land and on the sea floor

A volcanic eruption are a result of tectonic activity and it is when lava and gas are released from a volcano—sometimes explosively. The most dangerous type of eruption is called a 'glowing avalanche' which is when freshly erupted magma flows down the sides of a volcano. They can travel quickly and reach temperatures of up to 1,200 degrees Fahrenheit. Other hazards include ash fall, and lahars (mud or debris flows). Volcanoes often cause population displacement and food shortages.

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There are about 1500 potentially active volcanoes worldwide. When volcanoes erupt they can spew hot, dangerous gases, ash, lava and rock that can cause disastrous loss of life and property, especially in heavily populated areas. Volcanic activities and wildfires affected 6.2 million people and caused nearly 2400 deaths between 1998-2017

Volcanic eruptions can also cause secondary events, such as floods, landslides and mudslides, if there are accompanying rain, snow or melting ice. Hot ashes can also start wildfires.

Volcanic eruptions can impact climate change through emitting volcanic gases like sulfur dioxide, which causes global cooling as sulfur based particles together with volcanic dust and ash, reflect some of the solar energy from the sun back to space. It also emits volcanic carbon dioxide, which has the potential to promote global warming.

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https://www.youtube.com/watch?v=LQwZwKS9RPs

An educational video of how volcanoes form and what causes volcanic eruptions

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Volcanic eruption explained - Steven Anderson

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Negative and Positive effects of Volcanic Eruptions 

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Negative and Positive effects of Volcanic Eruptions 

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https://www.youtube.com/watch?v=tXHhceSYjtY

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Movie on the volcanic eruption that decimated the city of Pompeii

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Movie on the volcanic eruption that decimated the city of Pompeii

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"Pompeii" is a 2014 romance and historical disaster film that was inspired and based on the eruption of Mount Vesuvius in 79 A.D. that destroyed the city of Pompeii, a city of the Roman Empire. Serving as a reminder for one of the most horrific catastrophes to befall humanity, where the eruption of Mount Vesuvius, buried the city of Pompeii and stole the lives of as many as 16,000 individuals overall.

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Crater : A volcanic crater is a bowl -or funnel- shaped depression that usually lies directly above the vent from which volcanic material is ejected. Craters are landscape features that form during eruptions.

Caldera :  A caldera is a depression created after a volcano releases the majority of the contents of its magma chamber in an explosive eruption. Without any structural support below, the land around the erupting volcanic vent or vents collapses inwardly, creating the bowl-shaped caldera.

Vent : Vents may consist of a single, circular-shaped structure, a large elongated fissure and fracture, or a tiny ground crack. and it is where magma flows out of the volcano to the earth surface.

Magma Chamber : The location beneath the vent of a volcano where magma is stored prior to eruption. Also known as a magma storage zone or magma reservoir. As more magma is collected in the magma chamber, pressure builds up and causes an eruption

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Volcanoes vary in shapes and sizes due to the characteristics of lava. Low-silica lava has low viscosity while high-silica lava has high viscosity. Viscosity refers to the stickiness of lava or its resistance to flow.

Low-silica lava has a low viscosity which results in less explosive volcanic eruptions as this type of lava allows gases to escape easily and it flows through the vent easier before reaching the surface. Once on the earth's surface the outer layer of the cooling lava forms a thin crust.

High-silica lava is more viscous and traps gases easier. Causing a build up of pressure below the earth's surface . As magma rises the gases expand and this causes an outward explosion. The volcanic eruption then ejects lava, ash, rock fragments and gases into the surrounding environment.

This video explains the principle control of the violence of volcanic eruptions based on the viscosity of lava : https://www.youtube.com/watch?v=2iaqE0xmsHI

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Shield Volcanoes have gently sloping sides and have a broad summit. These are volcanoes that have been formed where low-silica lava has been ejected. Low-silica lava flows easily and spreads out over a large area and solidifies, as it does not trap much gases the volcanic eruptions are not explosive. The base of the volcano increases in size as lava accumulates with each volcanic eruption.

Shield Volcanoes are common near divergent plate boundaries where magma can rise directly from the mantle.

Example : Mount Washington in the USA

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Stratovolcanoes develop from successive volcanic eruptions and pyroclasts. Pyroclasts refer to ash, rock fragments and volcanic bombs ejected during a volcanic eruption.

After an initial eruption of Pyroclasts the next eruption ejects magma that overs the previous pyroclast and prevents it from erroding away. Over time this builds a high volcano with a slightly concave profile, meaning it is steeper at the top and gentler at the base. Secondary cones may also develop as magma from the vent seeps into the sides of the cone and erupts

Pyroclastic flow and lahars may result from volcanic eruptions. When pyroclasts mix with super heated gases from an eruption, it causes a pyroclastic flow at may reach speeds of 200m/s. Pyroclasts may also mix with water from melted ice in the vicinity or lakes to give rise to lahars, fast flowing mudflows that reach speeds of 40m/s.

Example : The eruption of the stratovolcano, Mount Pinatubo in the Philippines
https://www.youtube.com/watch?v=rjVZdlMlaiY

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The Pacific Ring of Fire, also known as the Circum-pacific Belt, is a region along the margins of several converging plate boundaries around the pacific ocean where most volcanic activity occurs. Its length is approximately 40,000 kilometers. It traces boundaries between several tectonic plates—including the Pacific, Juan de Fuca, Cocos, Indian-Australian, Nazca, North American, and Philippine Plates.

Seventy-five percent of Earth’s volcanoes—more than 450 volcanoes—are located along the Ring of Fire. Ninety percent of Earth’s earthquakes occur along its path, including the planet’s most violent and dramatic seismic events.

However, volcanoes are not just limited to the Pacifc ring of fire. As volcanoes also form in areas where tectonic plates diverge such as in the Atlantic Ocean and East Africa as magma rises to the surface.

This video gives us a brief introduction to the Pacific Ring of Fire as well as an explanation of why this Ring of Fire came to be as well as precautions taken by several countries : https://www.youtube.com/watch?v=DrwYtGf40hA

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Volcanic environments can be good locations for farming as lava and ash from volcanic eruptions break down to form fertile volcanic soil. Volcanic deposits are enriched in elements such as magnesium and potassium. When volcanic rock and ash weathers and are broken down over thousands of years, these elements are released, producing extremely fertile soils.

Thin layers of ash can act as natural fertilisers, producing increased harvests in years following an eruption. In response to frequent eruptions, some farmers have adapted their crops and farming styles to suit different types of ash.

Example : The volcanic soils of Java and Bali in Indonesia support the cultivation of crops like tea, coffee and rice and is the main reason why the two islands have been able to support a large rural population over many decades. Despite continuous use, these soils are more fertile than most non- volcanic areas

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Volcanic rocks can be rich in precious stones and minerals and can only be extracted from volcanic areas after millions of years. When the upper layers of volcanic rocks errode these resources can then be extracted.

Example : Diamonds are precious stones that may come from volcanic rocks. The old volcanic rocks at Kimberley in South Africa are one of the world's richest sources of diamonds. This video explains the history behind this diamond mine : https://www.youtube.com/watch?v=DAUUrGZcRCQ

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Volcanic areas offer a variety of activities for tourists to engage in. Tourists visit to hike and camp in the area or to simply enjoy scenery. Volcanic areas or rich in history and thus one can visit these areas to learn more about them.

Example : The ruins of Pompeii in Italy. The city of Pompeii was buried by layers of Ash following the eruption of Mount Vesuvius in 79 CE and the unearthed archaelogical site has revealed buildings, pottery and Mosaics left intact and it draws almost 3 million tourists each year.
https://www.youtube.com/watch?v=Gbr0QAX8XG8

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Geothermal energy is derived from the heat in the earth's crust. When groundwater in  the earth comes into contact with hot volcanic rocks, it heats up and erupts as hot water or steam. The hot water can then be harnessed to drive turbines to generate electricity which is cheaper for locals.

Example : Most of Iceland's electricity is generated from geothermal power due to the large amount of volcanoes in the country. Over 70% of homes are heated by volcanic steam in Iceland
https://www.youtube.com/watch?v=c0AzaJ6OzB0

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Volcanic materials produced by volcanic eruptions include lava and pyroclasts that consist of ash, rock fragments and volcanic bombs and can lead to widespread damage of property
Example : Lava has high temperatures of between 5000 to 1400 degree celsius and it burns through the areas it flows through

Low-silica lava moves rapidly and flows over long distances, causing damage to large areas. A pyroclastic flow can destory everything in its path with hot rock fragments ranging from ash to boulders travelling at speeds greater than 200m/s. Inhaling this hot ash can result in serious injury or even death

Finally, volcanic bombs of heated rock can fall in the vicinity around the volcano and damage property.
Example : The eruption of Kilauea in Hawaii since 1983 has destroyed many homes and highways

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Landslides can occur due to the structural collapse of a volcanic cone during a volcanic eruption. The landslides can range from a few rock fragments falling from the volcano to landslides of several hundreds of cubic kilometres. Landslides could obstruct the flow of rivers and cause floods, they could block roads and bury villages and farmlands.

Example : The eruption of Nevado del Ruiz in the Andez Mountains of South America in 1985 released a pyroclastic flow and the micture of this pyroclastic flow and glacial ice triggered lahars, which are flows of wet volcanic debris down the side of a volcano. The lahar engulfed the town of Armero and killed more than 20,000 people. This video documents the eruption of Nevado del Ruiz and the effects it had on the people of Columbia : https://www.youtube.com/watch?v=3XMS-quxdGg

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Ash particles ejected during a volcanic eruption can disrupt human activities over large distances from the volcano. Thick plumes of ash may eventually settle on the ground and block sunlight, suffocating crops and causing severe respiratory problems from people and animals.

Volcanic eruptions can also release possibly poisonous gases such as carbon dioxide, sulfur dioxide, hydrogen and carbon monoxide. Fine ash particles of less than 0.001mm can be carried by wind over thousands of kilometres and impact areas further away from the eruption source.

Example : The eruption of Eyjafjallajökull in Iceland 2010 produced extensive volcanic ash clouds containing tiny particles of abrasive glass, sand and rock. These particles posed serious danger to aircraft engines and structures and thus it caused a closure of air spaces over much of Europe and it costed the airline industry a total of US$1.8 billion.
https://www.youtube.com/watch?v=OyZHZhYDWNk