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A short class with Sarah and her students. The other ways are under More.
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Today we will explore Tacheletic Basalt and why it complicates excavation efforts. Can anyone tell me what they remember about this rock type?
Isn't it the type of basalt that's really thick and hard to work with?
Exactly, Student_1! Tacheletic Basalt forms thick layers on hillsides, making excavation quite difficult. Who can tell me what happens to this basalt as it gets excavated?
I learned that it can break into small pieces!
Right again! This breakage can lead to loss of evidence. Remember, we want to preserve history. One way to think about this is with the acronym B.R.E.A.K.: Basalt Rocks Easily And Kicks up dust!
Now, let's discuss the two types of basaltic lava: Aa and Pahoehoe. Student_3, can you describe what Aa lava looks like?
Aa lava is rough and has a rubbly surface!
That's right, and what about Pahoehoe lava, Student_4?
Pahoehoe is smooth and flows like liquid, right?
Perfect! To remember these, think of 'A' for 'Awkward' to recall Aa and 'P' for 'Pretty' for Pahoehoe. Both reflect their textures!
Besides the types of basalt, what natural processes affect these rock formations over time?
Is it weathering? Like how rocks get broken down?
Yes! Specifically, spheroidal weathering. Can anyone explain what that is?
I think it’s when the layers of rock erode in a round or chip-like manner?
Excellent, Student_1! Visualize it like chipping away at a spherical object. A way to remember this is with the phrase 'Round by Round, Nature Unwound!'
How does water seepage affect the caves formed in Tacheletic Basalt?
Is it damaging? Like causing cracks?
Exactly! Water can seep into cracks and facilitate more disintegration. Think of the mnemonic W.A.T.E.R.: Weakens And Turns Excavation Risky.
Finally, let's discuss how archaeologists document caves to prevent risks. What do you think this process involves, Student_3?
They probably look for cracks and analyze them, right?
Exactly! They categorize cracks by stability levels. Who remembers the classification system I mentioned?
Crack categories go from stable to unstable, like 1 to 5?
Right! Use the acronym S.U.B.S.T.A.N.C.E: Stable Unstable Breaks Show Terrible Archaeological Needs for Careful Examination!
A rock type that presents excavation challenges due to its fragmenting nature.
A rough surface type of basaltic lava.
A smooth, ropy surface type of basaltic lava.
A process of gradual erosion that creates rounded formations.
The process of documenting caves to understand structural integrity and risks.
Tacheletic Basalt, thick and tall, excavation risks we must recall.
Once upon a time, a cave explorer learned that some basalt is thick like a wall, and when it's wet, it can break and fall, leading to evidence lost to all.
Remember the acronym B.R.E.A.K. for basalt: Basalt Rocks Easily And Kicks up dust!
For weathering, think of 'S.W.E.L.L.': Spheroidal Weathering Erodes Layers Leading to loss.
Term
What is Tacheletic Basalt?
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Describe Aa Lava.
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What is Pahoehoe?
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What is Spheroidal Weathering?
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A type of basalt characterized by thick layers, its chemical properties react unfavorably with moisture.
Basaltic lava with a rough, rubbly surface.
Smooth basaltic lava with a billowy, undulating surface.
A natural process where rocks erode in a rounded or chip-like manner.
The gradual escape of liquid through pores or cracks.
This section discusses the geological characteristics of Tacheletic Basalt and its implications for excavation, highlighting the challenges posed during archaeological discoveries.
Focusing on Tacheletic Basalt, this section explores its properties, including how its softening nature during excavation can lead to loss of historical evidence. The section also details geological and geomorphological findings, including lava types and weathering processes, which impact archeological efforts.
The section emphasizes the challenges faced during the excavation of areas characterized by Tacheletic Basalt, particularly at Pitalkhora. Due to the thick layers of this basalt, excavation plans encounter significant restrictions. The basalt, when excavated, tends to fragment into smaller pieces, posing a risk of losing crucial archaeological evidence.
The text explains two distinct types of basaltic lava:
As these lavas cool, they form structural features including joints and hollow spaces that can then be leveraged for human habitation. Furthermore, there are horizontal layers formed by multiple lava flows over time, indicating the geological history of the region.
Significantly, Tacheletic Basalt's chemical properties create challenges for cave excavation, as interaction with moisture leads to disintegration, complicating preservation efforts. Additionally, the section elaborates on natural processes such as spheroidal weathering, through which rocks gradually degrade, and illustrates how water seepage affects the caves' structural integrity.
The section concludes with how archaeologists have documented and analyzed these caves, categorized the types of cracks affecting stability, and meticulously planned conservation efforts from 1954 to 2008.