Here's why:

* Low viscosity: Quietly flowing lava has low viscosity, meaning it's thin and runny. This allows it to spread out over large areas.

* Gentle eruptions: The eruptions are non-explosive and release lava steadily.

* Broad, gentle slopes: As the lava spreads, it forms a broad, gently sloping cone.

Some examples of shield volcanoes include:

* Mauna Loa in Hawaii

* Kilauea in Hawaii

* Olympus Mons on Mars (the largest volcano in the solar system)

It's important to note that while shield volcanoes are primarily formed by quiet lava flows, they can sometimes experience more explosive eruptions as well.