A grammar test for all.

1. Identify which is correct (use a comma or no?):

When Weatherill discovered Chaco canyon in 1897, aided by his Navajo guide, he stumbled upon the remains of a great, ancient civilization.

When Weatherill discovered Chaco canyon in 1897, aided by his Navajo guide, he stumbled upon the remains of a great ancient civilization.

According to most guides:

5. Commas separate descriptive modifiers of equal rank. If you can use adjectives interchangeably and can successfully insert the conjunction "and" between them, they are coordinate and require a comma.

Example:
Scientists will not predict the next activity of the fickle, explosive volcano.

So, either way it seems to be ok. I think you could go with or without the comma. It makes sense to say, "...he stumbled upon the remains of a great and ancient civilization." Thus necessitating the use of a comma.

2. Which is correct?

I learned that when the Pueblo Indians inhabited Chaco Canyon and the surrounding areas, there was a period of great rainfall which enabled them to live off the land through farming and the raising of livestock.

I learned that when the Pueblo Indians inhabited Chaco Canyon, and the surrounding areas, there was a period of great rainfall which enabled them to live off the land through farming and the raising of livestock.

Here is what one guide says:

2. Commas separate two independent clauses connected by a coordinating conjunction (and, or, nor, but, so).

Example:
Seven men were arrested on the east side, and ten more were taken into custody six hours later.

So it would seem that the comma is not necessary as they are not two independent clauses. You could not have: "I learned that the Pueblo Indians inhabited Choco Canyon." "And the surrounding areas." There is no subject-verb relationship in the second half of the sentence, therefore, the comma is not used.

3. One more example of the above rule:

Though the civilization has now disappeared, it is widely believed that the dwellings in the locale of the four corner states existed circa 900-1250 and featured five story buildings, mass graves and various building elements which were brought in from up to fifty miles away by hand.

Though the civilization has now disappeared, it is widely believed that the dwellings in the locale of the four corner states existed circa 900-1250, and featured five story buildings, mass graves and various building elements which were brought in from up to fifty miles away by hand.

Comma or no? I say no - again, following the comma in the second example, there is no subject. What featured five story buildings? What featured mass graves? There would most definitely be a comma if it said: "Though the civilization has now disappeared, it is widely believed that the dwellings in the locale of the four corner states existed circa 900-1250, and the civilization featured five story buildings, mass graves and various building elements which were brought in from up to fifty miles away by hand."

4. And our final example (comma or no?):

there was a period of great rainfall which enabled them to live off the land through farming and the raising of livestock rather than being forced to migrate with the food source

there was a period of great rainfall, which enabled them to live off the land through farming and the raising of livestock rather than being forced to migrate with the food source

URL2 says:

3. Use a pair of commas in the middle of a sentence to set off clauses, phrases, and words that are not essential to the meaning of the sentence. Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause.

Here are some clues to help you decide whether the sentence element is essential:

* If you leave out the clause, phrase, or word, does the sentence still make sense?
* Does the clause, phrase, or word interrupt the flow of words in the original sentence?
* If you move the element to a different position in the sentence, does the sentence still make sense?

If you answer "yes" to one or more of these questions, then the element in question is nonessential and should be set off with commas. Here are some example sentences with nonessential elements:

Clause: That Tuesday, which happens to be my birthday, is the only day when I am available to meet.
Phrase: This restaurant has an exciting atmosphere. The food, on the other hand, is rather bland.
Word: I appreciate your hard work. In this case, however, you seem to have over-exerted yourself.

I'm still undecided here, however, it appears that some think that if you see "which," it must be preceded by a comma.

Perhaps I just need to have someone who really knows what they're talking about comment here...

URL: tip Sheet-Comma Usage
URL2: Using Commas