English (Fire Operator) - 3

According to the passage, which of the following was crucial to the discovery of magnetic reversal?

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

The main purpose of the passage is to

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

Magnetic reversal refers to

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

One can infer from the passage that

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

The word 'trapped' in the passage is closest in meaning to

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.