Seventy percent of the earth is ocean and three percent is land.

Distribution characteristics of land and sea: land is concentrated in the northern hemisphere, and oceans are concentrated in the southern hemisphere.

Water hemisphere, land hemisphere: No matter how we divide any two equal-sized hemispheres of the earth, the ocean area is greater than the land area.

Related concepts: continent, island, peninsula, ocean, sea, strait, continent

seven continents

four oceans

Terrain: various undulating forms on the earth's surface

There are five basic land terrains: plains, plateaus, mountains, hills, and basins.

Two major mountain ranges on land

seabed topography

Changes in the sea

Evidence of land and sea changes

Reasons for changes in alignment: changes in the earth's crust, rise and fall of sea levels, human activities

Proposed by: German scientist Wegener

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main evidence

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Six major sectors

Movement conditions: The crust inside the plate is stable, and the crust at the plate boundary is active.

The world's two major volcanic and seismic zones