Here's why:

* Sharp Corners: Volcanic bombs are large pieces of ejected lava that solidify in mid-air, often taking on irregular, angular shapes as they cool.

* Blown out from the Inside: They are formed when molten lava is violently ejected from a volcano, often during explosive eruptions.

* Size: Volcanic bombs can range in size from a few centimeters to several meters in diameter.

Let me know if you have any other questions about volcanoes!