The field is about 100 years old.
( ( The field ) ( ( is ( ( ( about 100 ) years ) old ) ) . ) )
(ROOT (S (NP (DT The) (NN field)) (VP (VBZ is) (ADJP (NP (QP (RB about) (CD 100)) (NNS years)) (JJ old))) (. .)))
The field was made 100 years ago.
( ( The field ) ( ( was ( made ( ( 100 years ) ago ) ) ) . ) )
(ROOT (S (NP (DT The) (NN field)) (VP (VBD was) (VP (VBN made) (ADVP (NP (CD 100) (NNS years)) (RB ago)))) (. .)))