Final answer:
Coasts may advance seaward due to sediment deposition, sea level rise from global warming, and overwash from storm events that move sediments forward.
Step-by-step explanation:
Coasts may advance seaward as a result of several natural processes, including sediment deposition and changes in sea level. When sediments collect and build up along the shoreline due to river deposits, wave action, or other means, this can cause the coastline to extend outward. Additionally, sea level rise, mainly due to global warming, contributes to the reshaping of coastlines by melting glaciers and ice caps, which adds meltwater to the oceans and causes thermal expansion of the water as it warms. These combined effects can cause shorelines to be inundated, with changes in island size and potential loss of islands entirely.
Another contributing factor can include overwash, which occurs when waves rush over a coast during storms, depositing sand and other sediments on the other side, potentially extending the coastline. Some coasts may be protected from significant change due to their orientation or barriers like reefs, which can reduce the impact of waves and storm surges.