What was a negative effect of the columbian exchange on europe?

A negative effect of the Columbian exchange on Europe was the sand fleas arrival to the old world.

Explanation:

The majority of the negative effects were caused to the Americas, nevertheless, the Europeans also had their portion of negative effects. One of them was the sand fleas that inserted their eggs under the skin of the carrier and propitiated unknown infections as well as breakouts in different species. The Europeans carried them in themselves, in animals and even in the inventories of crops and organic tissue they transported to Europe. They also faced rural changes due to the introduction of new world plants to the old world and the modification of the fields lead them to ruin it for profit.

- three-quarters or two-thirds..

- "the constitution provides that an amendment may be proposed either by the congress with a two-thirds majority vote in both the house of representatives and the senate or by a constitutional convention called for by two-thirds of the state legislatures."

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well that depends on how deep the hole is. you'd first go through te crust of the earth, then the upper mantle, then the lower mantle then the outer core, then the inner cor then you'd be stuck in the core to melt.