Week 5 the third reading journal

"Great Dying" Lasted 200,000 Years

http://news.nationalgeographic.com/news/2011/11/111121-great-dying-permian-mass-extinction-science/

Summary

    According to a new study, Great Dying, the period about 252 million years ago, continued at least 200,000 years. This period made 90% living things on Earth extinct both on land and in the sea simultaneously. This time span was proved by analysis of fossils and chemical evidence of changes in Earth's carbon cycle in rocks fro south China to Tibet. This catastrophe was caused widespread wildfires, a scientist said. She found mass charcoal-rich and soot-bearing bed in sedimentary rock of the period. These rocks also proved that oxygen level on Earth declined rapidly during the the Great Dying because they found the tiny living-things' fossils on both side. Scientists thought that living things which could survive in such less oxygen had changed their structure smaller.
    But scientists wonder the mystery why the catastrophe occurred. Because they need more evidences to prove the coincidental extinction on land and in the sea. So far, they believe the reason why the massive extinction occurred coincidentally is supposed to be not only volcanic activities, but also an asteroid or comet impact.


My opinion
This article's subtitle is "Wildfires, disappearing oxygen HELPED kill off 90% of all life on Earth". I think it is interesting expression. If I were an writer, I would use "was forced to" instead of "helped". Is it the problem of my English skill or the intention of the writer toward scientists? I do not understand the intention of the usage "helped". As I remind, for scientist, the extinction might have been necessary incident. Anyway, I was astonished such huge wildfires continued over 200,000 years. The history of our planet is really mysterious.


Vocabularies
1)simultaneously
:adverb
:at the same time
:synchronously
:The couple of serious terrorism in the U.S. happened simultaneously on 9.11, 2000.


2)sedimentary
:adjective
:formed by the deposition of sediment
:No synonym
:I wonder how the sedimentary rocks are formed.


3)coincidental
:adjective
:existing or occurring simultaneously
:accidental
:The coincidental accidents made me sad.