Kaliadem - Geog investigation, identifying deposits and analyze impacts.

kaliadem is located at the base of Mt Merapi, 4km away from the peak. 
At the site, we had the opportunity to study the different types of intrusive and extrusive igneous rocks.

we were excited to be able to catch a superb view of Mt Merapi in the morning.

Amphibole (Black crystal with a 120 degree cleavage) indicate the presence of  water (Hydra minerals).  This tells us that there is a high possibility that a violent eruption happened in the area. Moisture in the minerals created more gas and bubbles, resulting in explosive eruption

Presence of lithic fragments in intrusive volcanic rock. 

Brown/orange stains on the rocks around the degassing hole, with steam still emitting from the hole.

The situation above suggested that a lot of heat is still being trapped by the rocks. The gas emitted from the hole is steam, and it contains a lot of moisture as oxidation is happening around the area, causing a brownish tint on the rocks. This shows that the eruption happened recently, and was likely a violent eruption due to the presence of large amount of moisture within the rocks.

Degassing happens after the eruption and not before, suggesting that previously gas was not able to escape due to the high viscosity of the magma, resulting in explosive eruption.

Possible investigation/inquiry questions
- Is it a recent or ancient eruption?
- Was the eruption violent or gentle?

Old vs New deposits. At the bottom we can see presence of new deposits, loose, homogenous materials with no vegetation. On the other side (top part), presence of old deposits with vegetation.

Pyroclastic deposits spread over a large, up to 15km away from the crater!! Can see the lahar flow at the left side of the middle part of the photo.

Coarse/Bigger materials such as boulders, rocks area deposited closer to the volcano. But lahar can follow the topography of the area and wash hugh boulders downstream, over long distances.

Hyperconcentrated lahar flow quickly increase their volume as they incorporate sediments of different sizes and weight along their travel paths. Highly erosive and destructive, strong enough to break and shift bridges as seen above.

Prambanan Temple – Effect of 2006 Earthquake

Prambanan temple – Unesco world cultural heritage

Background – With over 240 Hindu temples located near Piyungan, Prambanan is a Unesco World Cultural Heritage site and is more than 1100 years old. Earthquake resulted in extensive damage to this beautiful place.

Wreckage in Prambanan, after the 2006 earthquake devastated the area.

Yogyakarata Prambanan – Geological settings

Geology – Situated at the flat land between two hilly areas (West Progo Mountain and Southern Mountain), Prambanan is located at the foot of Mt Merapi and at the end of Opak River Fault, a 40 km secondary fault perpendicular to the main fault at the subduction zone where the Indo-australian plate descend beneath the Eurasian place. The left and right side of the fault moved at different speeds.

2006 Earthquake – Mag 6.3

More than 5000 dead, 83000 homes damaged and 1.5 million homeless in the densely populated Yogyakarta. Prambanan temple was also in a wreckage, with most of the shrines and temples being destroyed.

There used to be more than 240 temples and shrines. But only a few remained after the 2006 earthquake.

Why is the 2006 Earth so devastating, especially the area near Prambanan?

1.     The Earthquake in 2006 produced tremors along the Secondary fault (Opak river fault). Tremors along secondary fault lines are often shallow, less than 10km away from the surface. The impact of shallow earthquake can be quite severe despite the lower magnitude because the energy from the quake would have less time to dissipate, resulting in great damage to the area.

2.      Prambanan is located at the end of the secondary fault as seen in the figure. As such, Prambanan received the greatest impact as the seismic energy is concentrated at the end of the secondary fault.

3.      Prambanan is on the soft volcanic rocks of the deposits from Mt Merapi, which amplify and prolong shaking when there is earthquake. Half of the Prambana temple built on swamp filled with reclaimed soft soil, the other half on solid ground. As such, the earth resulted in a long crack in the middle, causing much devastation to the temple.   
4.   Wrong restoration of the Siva Temple before 2006 resulted in more harm – Before the 2006 earthquake, clay and cement were used to join the stone blocks, which is different from the ancient way of construction using interlock system. This proved to be a mistake as  the cement and clay are too rigid and does not allow flexibility in the structure, as such many temples crumbled and collapsed during the 2006 earthquake.

Interlock system used in the past, which proved to be more earthquake resistant since it allow the stones more flexibility and movement to counter the tremors from the earthquake.

Secondary impact on tourism.

Tourism is a key economic sector for Yogyakarta, providing employment and income directly and indirectly to thousands of people. Hundreds of craft villages that make souvenirs, arts and crafts were greatly affected. (Bali tourism board)

Locals walking around to pick up metal cans and
sell them to make a living.