Expansion and shrinking of wood
Wood of all types will expand when they absorb moisture and shrink when they lose moisture.
Expansion and shrinkage in woods
Trees are just like all other living organisms that consist mainly of water. When wood has just been cut, it will still have a very high level of moisture content and cannot be used as firewood or for woodworking. The wood has to be dried in either an open space or in an oven. Ideally, the wood should first attain the same humidity as its surrounding environment, before it becomes useful.
The expansion and contraction of wood is caused by the surrounding humidity than thermal factors. A higher humidity in the surrounding air will cause wood to expand whereas a lower humidity will cause the wood to shrink. The expansion of the wood will be greater along the growth rings of the wood and less pronounced or almost negligible along the length of the wood.
Be careful when removing the hot wooden blocks from the oven. Use gloves to protect your hands.