Final answer:
The three pieces of evidence for seafloor spreading are: the age of the seafloor, magnetic striping, and matching rock layers.
Step-by-step explanation:
There are three pieces of evidence for seafloor spreading:
- Age of the seafloor: The seafloor gets younger as you move away from the mid-ocean ridges. This suggests that new seafloor is being formed at the ridges and spreading apart.
- Magnetic striping: The seafloor is striped with alternating bands of normal and reversed magnetic polarity. These stripes mirror the pattern of Earth's magnetic field reversals. This supports the idea that new crust is being created and pushing older crust aside.
- Matching rock layers: Rock samples taken from the seafloor on either side of a spreading ridge show similarities in age, composition, and intensity of magnetism. This indicates that they were once connected and have been moving apart due to seafloor spreading.