The "Great Calamity" refers to a significant and devastating event in history, often associated with the Irish Potato Famine of the mid-19th century. This disaster led to the death of approximately one million people and caused another million to emigrate from Ireland. The famine was primarily caused by a potato disease known as potato blight, which destroyed the staple crop relied upon by a large portion of the population. The effects of the Great Calamity were profound, leading to widespread suffering and social upheaval. It highlighted issues of land ownership and food distribution in Ireland, as many landlords exported food while their tenants starved. The event remains a crucial part of Irish history, shaping national identity and influencing future generations.