SB 12.3.30

yadā māyānṛtaṁ tandrā
 nidrā hiṁsā viṣādanam
śoka-mohau bhayaṁ dainyaṁ
 sa kalis tāmasaḥ smṛtaḥ
Synonyms: 
yadā — when; māyā — deceit; anṛtam — false speech; tandrā — sloth; nidrā — sleep and intoxication; hiṁsā — violence; viṣādanam — depression; śoka — lamentation; mohau — and delusion; bhayam — fear; dainyam — poverty; saḥ — that; kaliḥ — the Age of Kali; tāmasaḥ — in the mode of ignorance; smṛtaḥ — is considered.
Translation: 
When there is a predominance of cheating, lying, sloth, sleepiness, violence, depression, lamentation, bewilderment, fear and poverty, that age is Kali, the age of the mode of ignorance.
Purport: 

In Kali-yuga, people are almost exclusively devoted to gross materialism, with hardly any affinity for self-realization.