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All Common Core: 7th Grade English Language Arts Resources
“Stone Trees”
Have you ever seen a stone tree? While the idea of a stone tree may sound fantastic, fallen trees can turn to stone in very specific circumstances, producing what scientists call “petrified wood.” “Petra” means stone in ancient Greek, so something “petrified” has been turned to stone. You may have heard the word “petrified” used to describe someone so scared that they have frozen as if turned to stone, but scientists use the word literally to refer to actual stone. Petrified trees are stone trees, not scared trees!
A Type of Fossil
Like ancient skeletons of dinosaurs and other organisms preserved in the earth, petrified wood is a type of fossil; however, there is a big difference between petrified wood and most fossils. Most fossils are imprints of creatures or partial remains of them, such as their skeletons. In contrast, the process of petrification recreates an entire preserved tree in stone. It’s very cool to see a petrified tree close-up, because it is still precisely life-size; you can get an idea of how big the tree was when it was alive, and even see individual tree cells that have been preserved. You can even count the tree rings in some petrified trees and estimate how old the tree grew to be before it was petrified.
From Tree to Stone
In order for a tree to become petrified wood, it must have died and been buried a very long time ago. This has to have happened in a specific environment, though, or petrified wood would not be so rare. The tree has to be buried in such a way that oxygen cannot get to its bark and wood. If oxygen can get to the tree, it will rot instead of turn to stone.
The environment has to have two more specific characteristics to produce petrified wood: there has to be water in the ground around the tree, and that water has to contain minerals. If mineral-containing water is present, water will go into and out of the tree’s cells and, over time, the minerals in the water will accumulate in the tree’s cells. When the tree’s cells eventually decay, the minerals are left. Petrified wood can be a rainbow of different colors, with each color corresponding to different elements in the tree’s preserving environment that affect the color of the minerals that form its stone.
Petrified wood is found all over the world, and there are even entire forests of petrified trees that you can travel to go see today. One national park in the United States, Petrified Forest National Park in Arizona, is famous for its many petrified trees. The next time you see a tree, remember, after a few million years in the right environment, it could turn to stone!
Passage 2: “The Petrified Forest of Arizona” by E.A. J. Seddon, Associate Editor, Southern Division in The Mountain States Monitor, September 1918.
The Petrified Forest of Arizona is an area covered with the fossil remains of prehistoric trees. The name “Petrified Forest” is somewhat of a misnomer: the word “forest” suggests standing trees, but these trees fell over long ago and have been preserved in stone. At one time, they formed part of a forest of gigantic trees. They proudly reared their heads above the surrounding country, but they were conquered and laid low by some force of nature.
Then began the process of embalming and preserving these fallen monarchs. They were buried thousands of feet beneath the bottom of an inland sea. This was a vast pickling vat where the wood was slowly converted into living gems. We can tell this because volcanic cones and mineral springs still exist in the area.
Water containing minerals slowly forced its way into the trunks and limbs and roots of the fallen monarchs under a terrific pressure. Eventually, the woody material was gradually replaced by silica, a type of rock. Iron oxides were present in the silica. These oxides created brilliant and beautiful brown, yellow, and red colors in the rock.
Eventually, the sediment containing the petrified trees was thrown up from nature’s subterranean chemical laboratory. The wrappings of the dead monarchs were slowly washed away by erosion and corrosion. Then the glorious sun shone upon the trees once again. They were no longer rulers of the kingdom of flora, but preserved for all time as agate, jasper, opal, and other forms of silica.
About which of the following points do the passages present the most different interpretations?
How petrified wood differs from dinosaur fossils
What causes the different colors in petrified wood
Whether petrified wood can be found in Arizona
What other materials besides wood can be petrified
The role that water plays during the petrification process
About which of the following points do the passages present the most different interpretations?
How petrified wood differs from dinosaur fossils
Whether petrified wood can be found in Arizona
What other materials besides wood can be petrified
The role that water plays during the petrification process
What causes the different colors in petrified wood
This question asks us to identify the point about which the authors' interpretations differ the most. They need not outright disagree about the point, but they need to claim different things about it or interpret it in different ways. Neither passage mentions other materials besides wood being able to be petrified, so "what other materials besides wood can be petrified" cannot be correct. "How petrified wood differs from dinosaur fossils" cannot be correct either, since only Passage 1 discusses this point. We can't say that the passages present different interpretations of an idea if only one passage mentions it! This leaves us with three answers:
- Whether petrified wood can be found in Arizona
- What causes the different colors in petrified wood
- The role that water plays during the petrification process
Both passages agree about the role that water plays during the petrification process. Passage 1 states, "If mineral-containing water is present, water will go into and out of the tree’s cells and, over time, the minerals in the water will accumulate in the tree’s cells." Passage 2 says, "Water containing minerals slowly forced its way into the trunks and limbs and roots of the fallen monarchs under a terrific pressure." These are very similar explanations, so "The role that water plays during the petrification process" can't be the correct answer.
The passages also agree about "whether petrified wood can be found in Arizona." In its last paragraph, Passage 1 states, "One national park in the United States, Petrified Forest National Park in Arizona, is famous for its many petrified trees." Passage 2 opens with the statement "The Petrified Forest of Arizona is an area covered with the fossil remains of prehistoric trees." (Its title can also help you infer that it is claiming petrified wood can be found in Arizona.) Thus, the passages agree about this point, too, making the related answer choice incorrect.
The correct answer—the statement about which the passages disagree most—is "What causes the different colors in petrified wood." Passage 1 says that "Petrified wood can be a rainbow of different colors, with each color corresponding to different elements in the tree’s preserving environment that affect the color of the minerals that form its stone." So, it says that the different colors are due to elements that affect the color of the minerals used to form the stone. Passage 2, on the other hand, mentions specific types of rock: "Eventually, the woody material was gradually replaced by silica, a type of rock. Iron oxides were present in the silica. These oxides created brilliant and beautiful brown, yellow, and red colors in the rock." Passage 2's interpretation of what causes different colors to appear in petrified wood is quite different from the explanation that Passage 1 provides, so this is the correct answer.
“Stone Trees”
Have you ever seen a stone tree? While the idea of a stone tree may sound fantastic, fallen trees can turn to stone in very specific circumstances, producing what scientists call “petrified wood.” “Petra” means stone in ancient Greek, so something “petrified” has been turned to stone. You may have heard the word “petrified” used to describe someone so scared that they have frozen as if turned to stone, but scientists use the word literally to refer to actual stone. Petrified trees are stone trees, not scared trees!
A Type of Fossil
Like ancient skeletons of dinosaurs and other organisms preserved in the earth, petrified wood is a type of fossil; however, there is a big difference between petrified wood and most fossils. Most fossils are imprints of creatures or partial remains of them, such as their skeletons. In contrast, the process of petrification recreates an entire preserved tree in stone. It’s very cool to see a petrified tree close-up, because it is still precisely life-size; you can get an idea of how big the tree was when it was alive, and even see individual tree cells that have been preserved. You can even count the tree rings in some petrified trees and estimate how old the tree grew to be before it was petrified.
From Tree to Stone
In order for a tree to become petrified wood, it must have died and been buried a very long time ago. This has to have happened in a specific environment, though, or petrified wood would not be so rare. The tree has to be buried in such a way that oxygen cannot get to its bark and wood. If oxygen can get to the tree, it will rot instead of turn to stone.
The environment has to have two more specific characteristics to produce petrified wood: there has to be water in the ground around the tree, and that water has to contain minerals. If mineral-containing water is present, water will go into and out of the tree’s cells and, over time, the minerals in the water will accumulate in the tree’s cells. When the tree’s cells eventually decay, the minerals are left. Petrified wood can be a rainbow of different colors, with each color corresponding to different elements in the tree’s preserving environment that affect the color of the minerals that form its stone.
Petrified wood is found all over the world, and there are even entire forests of petrified trees that you can travel to go see today. One national park in the United States, Petrified Forest National Park in Arizona, is famous for its many petrified trees. The next time you see a tree, remember, after a few million years in the right environment, it could turn to stone!
Passage 2: “The Petrified Forest of Arizona” by E.A. J. Seddon, Associate Editor, Southern Division in The Mountain States Monitor, September 1918.
The Petrified Forest of Arizona is an area covered with the fossil remains of prehistoric trees. The name “Petrified Forest” is somewhat of a misnomer: the word “forest” suggests standing trees, but these trees fell over long ago and have been preserved in stone. At one time, they formed part of a forest of gigantic trees. They proudly reared their heads above the surrounding country, but they were conquered and laid low by some force of nature.
Then began the process of embalming and preserving these fallen monarchs. They were buried thousands of feet beneath the bottom of an inland sea. This was a vast pickling vat where the wood was slowly converted into living gems. We can tell this because volcanic cones and mineral springs still exist in the area.
Water containing minerals slowly forced its way into the trunks and limbs and roots of the fallen monarchs under a terrific pressure. Eventually, the woody material was gradually replaced by silica, a type of rock. Iron oxides were present in the silica. These oxides created brilliant and beautiful brown, yellow, and red colors in the rock.
Eventually, the sediment containing the petrified trees was thrown up from nature’s subterranean chemical laboratory. The wrappings of the dead monarchs were slowly washed away by erosion and corrosion. Then the glorious sun shone upon the trees once again. They were no longer rulers of the kingdom of flora, but preserved for all time as agate, jasper, opal, and other forms of silica.
A friend of yours knows a lot about different types of rocks and is interested in learning about petrified wood. You know your friend would be most interested in the passage that includes the most detailed discussion of the types of rocks that form petrified wood. Which passage would you recommend your friend read, and why?
Passage 2, “The Petrified Forest of Arizona,” because it talks about silica and iron oxides.
Neither passage, because different types of rocks are irrelevant to the subject matter of either passage.
Passage 1, “Stone Trees,” because it talks about minerals.
Both passages, because they both discuss specific types of rocks.
Both passages, because they both discuss petrification.
A friend of yours knows a lot about different types of rocks and is interested in learning about petrified wood. You know your friend would be most interested in the passage that includes the most detailed discussion of the types of rocks that form petrified wood. Which passage would you recommend your friend read, and why?
Neither passage, because different types of rocks are irrelevant to the subject matter of either passage.
Passage 1, “Stone Trees,” because it talks about minerals.
Both passages, because they both discuss specific types of rocks.
Both passages, because they both discuss petrification.
Passage 2, “The Petrified Forest of Arizona,” because it talks about silica and iron oxides.
To answer this question correctly, you need to consider how each passage discusses types of rock. Specifically, you need to compare the level of detail used in each and pick out the one that goes into more detail about this particular topic.
Passage 1 mentions rocks in its fourth paragraph, in the section "From Tree to Stone":
If mineral-containing water is present, water will go into and out of the tree’s cells and, over time, the minerals in the water will accumulate in the tree’s cells. When the tree’s cells eventually decay, the minerals are left. Petrified wood can be a rainbow of different colors, with each color corresponding to different elements in the tree’s preserving environment that affect the color of the minerals that form its stone.
This passage talks about "minerals" in the water, a relatively general term, and says that the different colors of petrified wood are caused by "different elements . . . that affect the color of the minerals that form its stone." That doesn't seem like a lot of detail about different types of rocks, but let's consider Passage 2 and see how the two compare.
Passage 2 talks about rocks in its third paragraph:
Water containing minerals slowly forced its way into the trunks and limbs and roots of the fallen monarchs under a terrific pressure. Eventually, the woody material was gradually replaced by silica, a type of rock. Iron oxides were present in the silica. These oxides created brilliant and beautiful brown, yellow, and red colors in the rock.
Passage 2 also talks about "minerals" in the water forming the stone of petrified trees, but it also specifies that the wood is replaced by "silica, a type of rock." It then discusses how "iron oxides" in the silica "created" the colors in the rock. This passage goes into much more detail about types of rock than Passage 1 does because it mentions silica and iron oxides. "Passage 2, “The Petrified Forest of Arizona,” because it talks about silica and iron oxides" is the correct answer.
"Both passages, because they both discuss specific types of rocks" is not the correct answer because as we've seen, the passages differ in the specificity with which they discuss types of rocks. "Both passages, because they both discuss petrification" is not correct because this is even more general—while both discuss petrification, they vary in how they discuss types of rocks. "Neither passage, because different types of rocks are irrelevant to the subject matter of either passage" is incorrect because types of rocks are relevant to the subject matter of each passage, petrified wood and its formation.
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