Plate Boundaries

What are tides?

• Tides are caused by gravitational pull of the moon and the sun.

• The rise and fall of the tides play an important role in the natural world and can have a marked effect on maritime-related activities.

• Tides are one of the most reliable phenomena in the world. As the sun rises in the east and the stars come out at night, we are confident that the ocean waters will regularly rise and fall along our shores.

• Tides are very long-period waves that move through the oceans in response to the forces exerted by the moon and sun. Tides originate in the oceans and progress toward the coastlines where they appear as the regular rise and fall of the sea surface.

• When the highest part, or crest, of the wave reaches a particular location, high tide occurs; low tide corresponds to the lowest part of the wave, or its trough. The difference in height between the high tide and the low tide is called the tidal range.

New Zealand Volcanoes

• New Zealand lies on the boundary between two tectonic plates. When the sub-ducting plate melts the buoyant magma can come to the surface and erupt. New Zealand has many volcano types, three main types are recognised. Eruptions are different depending on the type of magma.

• Inside the Earth there is a red-hot liquid rock, called magma. Volcanoes happen when magma rises to the surface of the earth, which causes bubbles of gas to appear in it. This gas can cause pressure to build up in the mountain, and it eventually explodes.

• When the magma bursts out of the earth, it is called lava.

Why New Zealand has active volcanoes

• Like earthquake activity, volcanoes in New Zealand usually occur along the plate boundary. Beneath New Zealand, the Pacific plate is pushing into the Indo-Australian plate and is being forced down into the Earth’s mantle. This creates a zone of subduction where the plate melts. Magma rising from this “subduction” zone produces a line of active volcanoes known as a volcanic arc. Most of New Zealand’s active volcanoes are caused by this process.

• New Zealand’s volcanoes are part of a larger zone of active volcanism at plate boundaries that rim the Pacific Ocean – the "Pacific Ring of Fire".

Reason for Seasons

• Earth’s tilted axis causes the seasons. Throughout the year, different parts of Earth receive the Sun’s most direct rays. So, when the North Pole tilts toward the Sun, it’s summer in the Northern Hemisphere. And when the South Pole tilts toward the Sun, it’s winter in the Northern Hemisphere.

• Earth's axis is an imaginary pole going right through the center of Earth from "top" to "bottom." Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth's surface gets some of each.