填空题.Metamorphic Rocks The three main types of rocks are igneous, sedimentary, and metamorphic. Of those, metamorphic rocks, which include schist, slate, marble, gneiss, quartzite, and lapis lazuli, are the most complex because they are formed when other rocks are subjected to intense heat and pressure. They all begin as igneous, sedimentary, or other metamorphic rocks, but then their mineral composition is transformed by intense heat and pressure deep underground. On some occasions, they may be changed through tectonic forces when the plates comprising the Earth's crust collide. There are both foliated and non-foliated metamorphic rocks. The term foliate refers to the visible colored bands present in some metamorphic rocks, so foliated rocks have these bands while non-foliated ones do not. ❶The creation of these two types of metamorphic rocks is the result of the different ways that pressure acts on the original rocks before they are transformed. ❷Foliated metamorphic rocks have pressure applied on a single plane, or direction, while non-foliated metamorphic rocks have pressure from several directions at once or from several directions at differing times, ❸The main result of this pressure is the recrystallization of the minerals in the original rocks.❹ Slate is a common type of foliated metamorphic rock that is produced from the sedimentary rock shale. Heat and pressure transform the clay minerals in shale to become mica, which is found in slate. Schist is another example of a foliated metamorphic rock. ❺It contains high levels of mica, which allows it to be broken up into thinner pieces. ❻Two common non-foliated metamorphic rocks are marble and quartzite. Marble is formed from limestone, a type of sedimentary rock. ❽It is regularly found in places where two of the Earth's plates are colliding and applying great pressure against each other. Under this pressure, the calcite crystals in limestone transform from being small, loose crystals to being larger, more interlocking crystals. Quartzite forms in much the same way as it changes from sandstone, another sedimentary rock. The loose sandstone crystals undergo an interlocking, binding transformation to create quartzite, a tougher and more durable rock. *recrystallization: the act of becoming crystal again *interlocking: interlaced; connected with one another
填空题7. Look at the four squares [❶-❹] that indicate where the following sentence could be added to the passage. The bands can be easy to see in rocks such as gneiss but are not as apparent in slate and phyllite. Where would the sentence best fit?
填空题8. Look at the four squares [❺-❽] that indicate where the following sentence could be added to the passage. The absence of bands makes it appealing to look at, so sculptors commonly utilize this material to make statues with. Where would the sentence best fit?