Tenerife
Each year, Truro School Geology Department run a week-long field course to Tenerife, encompassing the last few days of the Autumn Term and start of the Christmas Holidays. Click here for an introduction to the geology of Tenerife, showing how our fieldwork locations fit in to the geological evolution of the island. The Geologist's Association Guide by Gill and Thirlwall (2003) is highly recommended as an introduction to the geology of the island.
Itinerary for 2012
11th Dec Arrival. Puerto de Santiago and Los Gigantes – shield building day.
12th Dec A day spent studying the products of the evolved magma chamber of Las Cañadas volcano in the Bandas del Sur. San Miguel, Chimiche Quarry, La Cisnera - pumice day. Conveniently, during this day, the volcanic rocks which we study are from increasingly explosive eruptions.
13th Dec Walking down Teide – lava textures and modern volcanism.
14th Dec Icod, Garachico, Santiago del Teide and Masca - lava tubes, historic volcanism, then new and old basalt series.
15th Dec Coursework day at Tajao Quarry (at the weekend to ensure no quarry vehicles are working).
16th Dec An optional walk to the caldera rim from north of Vilaflor, with stunning views of the Caldera, Teide and Roques de Garcia.
17th Dec Los Roques de Garcia walk, the Caldera and dorsal ridge volcanism including a section near Montana Negra and view of the Orotava valley and visitors centre – Las Canadas and landslips day.
For a map of the circular walk at Los Roques de Garcia.
There are other 2011 Tenerife photographs in my Tenerife set on Flickr.
And for whatever they are worth, here is a link to my field notes, with spelling errors, incorrect information and speculation. If you are really interested in the geology of Tenerife, the book to buy is actually the Geological Association Guide No. 49 by Robin Gill and Matthew Thirlwall.
Practical ideas:
Terminal velocity calculations
Analysis of air fall deposits from the Granadilla pumice using Stokes's Equation for calculating the terminal velocity of falling spheres with laminar flow as approximations for the lithic and pumice fragments. - no good. I tried some calculations and the settling velocities are ridiculously high because the flow is turbulent (Reynolds number >0.1). There is an alternative equation in wikipedia http://en.wikipedia.org/wiki/Drag_(physics) for potato shaped objects, which gives a terminal velocity of 7 m/s for a 250 kg/m3 2.5 cm diameter pumice particle and the same terminal velocity for a 2 mm diameter 3000 kg/m3 basaltic lithic fragment - that looks more reasonable to me (7 m/s is 25 km/hr). It may be that the roughness of the pumice will further reduce the terminal velocity, but at least the results would be reasonably consistent with the Granadilla Pumice particle sizes!
According to the same equation, a 6 cm solid basalt volcanic bomb would reach a terminal velocity of 38 m/s or 137 km/h or 86 mph. A 40 cm block could achieve 100 m/s, which is 360 km/h or 225 mph. Using the equations of motion, it would need to fall at least 500 m to accelerate to 100 m/s (ignoring air resistance). In a Strombolian eruption, particles can be ejected tens to hundreds of metres into the air, so the 100 m/s terminal velocity for a 40 cm diameter bomb is an upper limit, but it does explain why many of the bombs are broken on impact. Using the equations of motion, the time of flight for this 40 cm bomb would be about 20 s, which is not very long for the breadcrust bomb to solidify before it hits the ground.
Lateral variation in pumice
Comparison of the Granadilla pumice between Chimiche Quarry and Tajao Quarry. Particularly thickness of the deposit, particle-size distribution using accurate measurements with calipers and the percentage of lithics and pumice (sampling with quadrats?).
Lateral variation in block and ash flow deposits
Measurement of the maximum and average particle size moving laterally and vertically through the block and ash flow deposit at Barranco del Azucar and Tajao Quarry.
Investigation of atmospheric pressure changes
Use of a gas syringe to examine the effect of reduced pressure moving from sea level to the Teleferico station near the top of Mount Teide.
Altitude of Teide = 3718m
Altitude of Los Gigantes = sea level (0 m)
Temperature on Teide = 10oC
Temperature in Los Gigantes = 25oC
Pressure on Teide approximately 60 kPa
Average sea-level pressure is 101.325 kPa
http://en.wikipedia.org/wiki/Atmospheric_pressure
Starting with a volume of 100 cm3
P1V1/T1 =P2V2/T2
101 x 100 / 298 = 60 x V2 / 283
V2 = 283 x 101 x 100 / (298 x 60)
V2 = 160 cm3
So the final volume for the top of Teide should be 60% higher than at the start, given a 15oC temperature drop.
Investigation of cooling with altitude and depth
Relationship between temperature and altitude travelling up Teide and down into the lava tubes. GPS gives altitude - can we calibrate it against any trig points?
As an average, the International Civil Aviation Organization (ICAO) defines an international standard atmosphere (ISA) with a temperature lapse rate of 6.49 K(°C)/1,000 m (3.56 °F or 1.98 K(°C)/1,000 Ft) from sea level to 11 kilometres (36,000 ft). http://en.wikipedia.org/wiki/Altitude
So, at 3718m, the temperature should be 24°C lower, which is why there is often snow on Teide. Let's hope for a repeat of the 2011 weather, as it was positively balmy on the mountain top!
Investigation of temperature with depth in a fumerole
Measurement of temperature against depth for the volcanic fumerole between the teleferico station and viewpoint for Pico Viejo using a temperature probe attached to a steel tape measure.
Investigation of change in boiling point with altitude
Measurement of the boiling point of water using a solid-fuel burner near the Teleferico station on Mount Teide.
According to Wikipedia, the boiling point of water at 4000m should be 87.3°C. That should be easy enough to measure with a digital thermometer and a small solid-fuel camping stove. Now where can I get the fuel for that in Tenerife?
Photography
360x180 degree panoramic photos at Los Gigantes, San Miguel, Roques de Garcia, Pico Viejo, Teleferico.
Gigapan photographs of the Tajao Quarry, both sections.
Investigation of changes in air resistance with altitude
Investigation of the change in air resistance with altitude using either a damped pendulum or a ping-pong-ball / sponge-ball gun.