The movement that contributed to a split in the Indian National Congress resulting in the emergence of `moderates` and `extremists` was the Swadeshi Movement.

The Swadeshi Movement was launched in 1905 as a response to the partition of Bengal by the British colonial administration. The movement aimed to promote the use of Indian-made goods and boycott British goods as a means of protest. The movement gained widespread support and led to the emergence of two factions within the Indian National Congress.

The `moderates` were led by leaders such as Dadabhai Naoroji, Gopal Krishna Gokhale, and Surendranath Banerjee. They advocated for a more gradual and constitutional approach to achieve self-rule and believed in dialogue with the British government.

The `extremists,` led by leaders such as Bal Gangadhar Tilak, Lala Lajpat Rai, and Bipin Chandra Pal, took a more radical approach. They demanded complete independence from British rule and were more willing to use militant means to achieve their goals.