1. Minor Forms of Extrusive Activity

2. Learning Goals Knowledge To know what are the minor forms of extrusive volcanic activity Understanding To understand how these minor extrusive features are created Skills Photograph interpretation Text comprehension

3. Geysir – click the image

4. Strokkur, Iceland

6. Geysers are hot springs that erupt periodically. Water in the lower crust is heated by rocks and turns into steam; pressure increases and the steam and water explode onto the surface. The ingredients needed for geyser activity are: heat, water, and underground rock hard enough to withstand intense pressures.

8. How Geysirs work - click the image How Geysirs work - click the image

9. A hot spring is a spring that is produced by the emergence of geothermally heated groundwater from the Earth's crust. There are hot springs all over the earth, on every continent and even under the oceans and seas. Other features

10. Mudpot – click to view! Boiling mud: hot water mixes with mud and surface deposits Example: Lassen Volcanic Park

11. A fumarole is an opening in Earth's crust, often in volcanic regions, which emits steam and gases such as carbon dioxide, sulphur dioxide, hydrochloric acid, and hydrogen sulphide. Fumaroles escape through Fourpeaked Glacier covering Fourpeaked Volcano in Alaska September 24 th 2006 Fumaroles escape through Fourpeaked Glacier covering Fourpeaked Volcano in Alaska September 24 th 2006

12. The name solfatara is given to fumaroles that emit sulphurous gases. Fumarole at Rincon de la Vieja Volcano National Park in Cost Rica

13. The name solfatara is given to fumaroles that emit sulphurous gases. Sulfurous fumaroles on Vulcano, Italy

14. Close-up view of the solfatara at Ijen, Indonesia with fumarole temperatures of more than 220°C.

15. Fumaroles may occur along tiny cracks or long fissures, in chaotic clusters or fields, and on the surfaces of lava flows and thick deposits of pyroclastic flows.fissures Fumaroles may occur along tiny cracks or long fissures, in chaotic clusters or fields, and on the surfaces of lava flows and thick deposits of pyroclastic flows.fissures Copahue volcano, Chile/Arg entina

16. A fumarole field is an area of thermal springs and gas vents where magma or hot igneous rocks at shallow depth are releasing gases or interacting with groundwater. Furnas Fumarole Field, the Azores From the perspective of groundwater, fumaroles could be described as a hot spring that boils off all its water before the water reaches the surface.

17. Hverarönd sulphuric mud pools (solfataras) The ground is unstable there and you cannot walk everywhere. Blue-grey mud is boiling and produces small or big (depending on water content) bubbles that burst. Hverarönd sulphuric mud pools (solfataras) The ground is unstable there and you cannot walk everywhere. Blue-grey mud is boiling and produces small or big (depending on water content) bubbles that burst. The ground is yellow and reddish and the noise from an abandoned hot water well is penetrating. The smell of sulphuric dioxide is everywhere. The ground is yellow and reddish and the noise from an abandoned hot water well is penetrating. The smell of sulphuric dioxide is everywhere.