Big Black Boring Rock : Essays On Northwest Geology
Jaiker Edouard
Bulldozers work in a marble quarry in Thásos, Greece. The Earth's heat and pressure alter limestone into marble, which can range in color from black to white. The ancient Greeks recognized marble's durability, using it to build the Parthenon in Athens. Marble, a metamorphic rock, forms when limestone re-crystallizes.
As far as the science goes, it was just awful (and it got worse with the newest revision of the Foundations Guide). There were something like 4 weeks in Cycle 1 where the kids spent the entire science time looking at rocks. Now I am fascinated by geology, but 4 weeks in a row of looking at rocks with a magnifying glass was just too much.
"When we got to Kirkwood and Whitewater Lake, we took our first taste of what seemed to be the two obvious main rock types that were present, to get a sense of what we're dealing with," said Squyres. "But rather than trying to tackle the nearest interesting looking problem in-depth, we wanted to get the big picture first," he explained. "It's just a sensible way of doing of geology. So we started at Whitewater Lake and we're going to finish at Whitewater Lake, and we will see what we see," he said.
From Big Nickel, the rover drove on, heading northwest. She put 13.02 meters (42.72 feet) on her rocker bogie on 3103 (October 16, 2012) before she stopped at Coleman. This mound appears to be exposed by a small crater downslope, and the MER scientists noted boxwork again.
As Opportunity has made her way west and now as she begins to head south on her loop around Matijevic Hill, she is roving back into familiar geology. "We started midway up the hill on Whitewater and drove north for 40 to 50 meters (131.23 to 164.04 feet) and were seeing fine-grained, light-toned outcrops [like Whitewater Lake] with possible veins embedded in the rocks," recounted Guinness. "Then we turned to the west and headed up Matijevic Hill and about halfway up we started seeing rocks that look familiar to those we saw when we first drove onto Cape York, like Chester Lake, the rock that had lots of embedded coarse-grained glass in it."
The excavation of tunnels and mine galleries, apart from dewatering by pumping, may cause dramatic changes in the local hydrogeology, leading to the formation of sinkholes (Bonetto, Fiorucci, Formaro, & Vigna, 2008; Marinos, 2001; Milanovic, 2004; Vigna, Fiorucci, Banzato, Forti, & De Waele, 2010; Wang, You, & Xu, 2008). The interception of conduits and cavernous rock by excavations performed below the water table may result in dangerous inrushes of water under pressure. The drainage of the aquifer towards underground artificial openings may lead to uncontrolled flooding of the excavation, rapid lowering of the water table, suspension of water supply from wells, enhanced internal erosion, and the development of sinkholes. In numerous mine districts in China, water inrushes and instability problems are especially common when the excavation works intercept pervious and mechanically weak breccia pipes rooted in deep-seated cavities developed in limestone or evaporites (Daoxian, 1987; He, Yu, & Lu, 2009; Li & Zhou, 1999; Lu & Cooper, 1997; Yin & Zhang, 2005). In northern Spain, the excavation of deep tunnels for a high-speed railway through a structurally complex karst aquifer caused the rapid lowering of the groundwater level and the occurrence of sinkholes in a river, functioning as ponors. The swallow holes have beheaded the downstream section of the river and captured the upstream section through karst conduits (Valenzuela et al., 2015). Sinkhole hazards may be particularly severe when fresh water flows into salt mines coming from an adjacent or overlying aquifer (Andrejchuk, 2002; Gowan & Trader, 2003; Kappel, Yager, & Todd, 1999) or from a surface water body (Autin, 2002; Lucha, Cardona, Gutiérrez, & Guerrero, 2008a). The highly aggressive water may cause massive dissolution of salt and uncontrollable sinkhole occurrence, leading to the abandonment of the mine. In the Cardona salt diapir, in northeastern Spain, the interception of a phreatic conduit by a shallow salt mine gallery (whose final goal was the disposal of hazardous wastes) caused the inflow of freshwater from a nearby river, rapid dissolution, formation of numerous collapse sinkholes, and ultimately the abandonment of the mine.