It's not accurate to say that a *part* of Earth is an island. An island is a landmass that is surrounded by water.

Here are some ways to think about this:

* Earth is a planet. It's a large sphere of land and water.

* Islands are a feature of the Earth's surface. They are individual landmasses that are smaller than continents.

So, instead of saying "part of Earth is island," you could say:

* "There are many islands on Earth."

* "Islands are found in all the world's oceans."

* "Some islands are volcanic, while others are formed by erosion."

Let me know if you have more questions!