Earth Science

 

ANSWER KEY: EVALUATION 1.3 1. How do does es a vesicular vesicular texture texture iin n a volcanic volcanic rock devel develop? op?

 Answer: As magma rises up to the surface, it is subjected to decreasing pressure, allowing dissolved gases to come out of the soluon forming gas bubbles. When the magma reaches the surface (as lava) and cools, the rock solidies around the gas bubbles. The bubbles are then preserved as holes or vesicles. Also, the texture can also be formed thru the rapid escape of gases. 2. Explai Explain n why v vesicul esicular ar te texture xture iiss not associated associated w with ith pe perido ridotes. tes.

Answer: Peridotes are intrusive rocks formed beneath the earth’s surface and the high pressure condions prevent gases from forming and escaping. 3. How do cl clasc asc ro rocks cks dif difer er ro rom m non-clasc non-clasc rocks rocks in terms terms o process process o ormao ormaon? n?

Answer: Clasc rocks form from rock fragments transported away from their source by wind, water, gravity or ice rather than by chemical processes such as precipitaon or evaporaon. 4. Explai Explain n how th the e physi physical cal eature eaturess o se sediment dimentss change during transpo transport. rt. 

Answer: The farther the sediment is transported, the longer the transport takes, and the smaller, more rounded and smoother the sediment becomes. 5. What do b bue ueri ries es and metam metamorp orphic hic rocks rocks ha have ve in common common? ?

Answer: Bueries and metamorphic rocks both undergo change from an earlier form (caterpillar for buery, parent rock for metamorphic rock) to a new one. 6. Can a miner mineral al be orm ormed ed in more th than an one process? process? I yes, yes, give exa example. mple. I no no,, explai explain n why.  

Answer: Yes. (Examples may vary) Gypsum can form as a precipitate from evaporang water, but also associated with volcanic regions where limestone and sulfur gases from the volcano have interacted. Copper may commonly be deposited as a disseminated hydrothermal deposit but can also be formed as a stratabound ore. 7. Discuss the diference diference betwee between n a magma magmacc ore deposit deposit an and d a hydrotherma hydrothermall deposit. deposit.

Answer: Magmac ore deposits are formed from dierent magmac processes such as crystal seling or crystal fraconaon. 8. What iiss the importance importance o the the diferent diferent stages o explora exploraon? on?

Answer: The dierent stages of mineral exploraon allow the investor to systemacally evaluate the potenal and marketability of having a mineral project. Knowledge about the project is increased at every stage, and this knowledge serves as the basis whether to proceed with the project or not. 9. An openopen-pit pit mine may in the the uture be conv converted erted into into an unde undergroun rground d mine. W Why hy would tthis his happen?

Answer: When all the minerals at or near the surface have been extracted, and when the lateral extent of the project area cannot hold the stability of slopes as mining gets deeper, the only way to mine the deeper extent of the orebody is to go underground. 10. Enumer Enumerate ate several several ways to rehabilit rehabilitate ate a mined-out area. area.

Answer: Topsoil replacement using uncontaminated soil; reintroducon of ora and fauna; neutralizing acidic waters; backlling and sealing underground mines; changing the slope of impacted area to reduce erosion; etc.