This is called the naimittika, or occasional, annihilation, during which the original creator, Lord Nārāyaṇa, lies down upon the bed of Ananta Śeṣa and absorbs the entire universe within Himself while Lord Brahmā sleeps.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
एष नैमित्तिकः प्रोक्तः प्रलयो यत्र विश्वसृक् । शेतेऽनन्तासनो विश्वमात्मसात्कृत्य चात्मभूः
eṣa naimittikaḥ proktaḥ pralayo yatra viśvasṛk | śete'nantāsano viśvamātmasātkṛtya cātmabhūḥ
SB 12.4.4